Easy Mars Bar Slice Recipe

Some recipes don’t whisper for your attention they sprint into the room, waving chocolate and caramel and shouting your name. That’s how I feel about a good mars bar slice recipe. It’s everything we love about a school-fete tray bake: no oven, five-ish pantry ingredients, and a dramatic chocolate top that cracks beautifully when you cut it.

If you’ve been searching for a version that sets firmly without going rock-hard, cuts cleanly, and tastes just like the ones you remember from tuckshop days, you’ve found it.

In this guide I’ll show you exactly how to make this Australian mars bar slice recipe in your own kitchen. We’ll talk about the right bar-to-butter ratio (so it’s chewy, not greasy), how to melt without splitting, why a pinch of salt turns the flavour from sweet to sophisticated, and the trick to glossy chocolate that slices like a dream. Whether you typed in mars bar slice or “Mars Bar slice recipe Australia,” this is the method I teach friends who want a foolproof tray that disappears at morning tea.

By the end you’ll have a mars bar slice recipe that’s simple enough for the kids to help with and reliable enough to bring to a fundraiser, office shout or dessert platter at your next BBQ. Bonus: you can make it the day before, so it’s ready when you are.

What Exactly Is Mars Bar Slice?

At its core, Mars Bar Slice is a no-bake chocolate crackle’s softer, chewier cousin. Classic Aussie pantry alchemy: melt chopped Mars Bars with butter and golden syrup, fold through Rice Bubbles (Rice Krispies), press into a lined tin, then pour on a layer of melted chocolate. Chill, slice, devour. Our Australian recipe leans into the caramel-nougat core of the chocolate bars, which melts into the butter to create a fudgy base that binds the cereal without turning it soggy. It’s nostalgic, wildly satisfying, and it packs and freezes like a champ.

You’ll find variations everywhere some add coconut, some swirl dark chocolate on top, some go extra with Maltesers. The version below is the classic I grew up with, tuned over years of bake sales and birthday parties so that it sets perfectly even on warm days.

Why This Mars Bar Slice Recipe Works

• Correct ratios. Too much butter and the base tastes greasy; too little and the slice crumbles. The quantities here give you chewy, cohesive squares with a gentle snap from the cereal.
• Gentle heat. Melt the bars low and slow so the nougat doesn’t seize. We use a double boiler (or heatproof bowl over a pot) to keep everything silky.
• Set-but-soft top. A touch of neutral oil in the chocolate topping stops it from shattering when sliced. It cuts clean, with appetising layers.
• Balanced sweetness. A pinch of sea salt and optional cocoa deepen the flavour so it tastes like a grown-up treat, not just sugar.
• Make-ahead friendly. The slice improves after a short chill. It travels well and freezes perfectly.
• Flexible add-ins. Coconut, Milo, peanuts or Coco Pops—this method handles them all.

I call this my “right-first-time” mars bar slice recipe. Follow the cues and you’ll nail it.

Ingredient Deep-Dive (And Smart Substitutions)

Mars Bars

Standard Australian Mars Bars are 47–53 g each; you’ll need enough to make 270 g (I use 6 × 47 g bars). If yours are larger, adjust accordingly. Chop into small pieces so they melt evenly. Yes, other caramel-nougat bars work, but Mars Bars give the iconic flavour.

Butter

Unsalted butter lets you control the salt. If you only have salted, reduce the added salt. Avoid margarine; it won’t set as clean.

Golden Syrup

This is the Australian magic—golden syrup adds a toffee note and helps the base stay chewy. Honey works in a pinch, but the flavour will change.

Rice Bubbles (Rice Krispies)

The classic cereal for light crunch. You can swap Coco Pops for a double-choc vibe or use half-and-half. If adding coconut or Milo, reduce cereal slightly so the base still binds.

Milk Chocolate (Topping)

Milk chocolate tastes like childhood. Dark chocolate gives a more grown-up edge. Either way, use decent eating chocolate and add 1–2 teaspoons of neutral oil (or a teaspoon of copha) to help with slicing.

Extras (Optional but Great)

• Pinch of fine sea salt (heightens caramel notes)
• 1 tablespoon cocoa (deepens colour and flavour)
• ½ cup desiccated coconut or chopped roasted peanuts (texture)
• Mini marshmallows or Maltesers (party energy)

Tools, Tin and Temperature

• Tin: 20 × 30 cm slice tin (8 × 12 in). If you only have 20 × 20 cm, the slice will be thicker; add 2–3 minutes extra chill time before topping.
• Lining: Grease lightly and line with two strips of baking paper so you can lift the slab out.
• Heat: Use low heat or a double boiler to melt bars and butter. Avoid the microwave unless you’re experienced—it’s easy to overheat.
• Stirring: A silicone spatula is perfect; it scrapes the bowl clean.
• Cutting: Warm a large sharp knife under hot water, dry it, and slice in confident downward strokes.

The Rhythm (Step-By-Step Cues You Can Trust)

1. Chop and melt. Gently melt butter with chopped Mars Bars and golden syrup, stirring until the nougat ribbons dissolve.
2. Balance the base. Stir in a pinch of salt (and cocoa if using).
3. Fold in cereal. Tip in Rice Bubbles and mix until every piece glistens—no dry pockets.
4. Press and chill. Press firmly into a lined tin (use baking paper on top to avoid sticky fingers). Chill 15–20 minutes—just enough to firm before topping.
5. Top and set. Melt chocolate with a teaspoon of neutral oil. Pour over base and smooth. Chill 45–60 minutes until set but not rock-hard.
6. Slice. Lift out, warm your knife and cut into neat squares or bars. Store chilled.

That’s the whole mars bar slice recipe in a heartbeat.

A Little Story (The Fete That Sold Out in Seven Minutes)

When my son was in Year 3, I made three trays of this slice for the school fete. I cut generous squares and priced them too low—rookie mistake. The first customer took a bite, turned around and bought an entire tray for the volunteers in the sausage sizzle tent. We sold out in seven minutes. Two parents messaged that night asking for “Ella’s mars bar slice recipe (the exact one please).” I sent them this version, ratios and all. It’s been doing the rounds at our school ever since.

Variations You’ll Actually Make

• Salted Peanut Crunch: Add ½ cup roasted peanuts to the base and sprinkle flaky salt over the chocolate top.
• Milo Swirl: Stir 2 tbsp Milo into the melted Mars Bar mixture; drizzle a Milo-milk paste over the chocolate top and feather with a skewer.
• Coco Pops Version: Swap half the Rice Bubbles for Coco Pops and use dark chocolate on top.
• Coconut Rough: Fold ½ cup desiccated coconut into the base; top with a mix of milk and dark chocolate.
• Festive Bars: Press mini marshmallows into the warm chocolate topping and scatter with crushed candy canes or coloured sprinkles.
• Gluten-Free: Use certified GF puffed rice cereal and ensure your chocolate is GF.
• Thermomix or One-Bowl: You can melt the bars and butter in the Thermomix on low (or a microwave at 50% power in short bursts) if you’re careful not to overheat.

Storage, Freezing and Transport

• Fridge: Store in an airtight container for up to 1 week.
• Freezer: Freeze slices in layers with baking paper between for up to 2 months. Thaw at room temperature 20–30 minutes.
• Hot Weather: Keep chilled until serving; transport in a cooler bag with an ice brick.
• Lunchboxes: Pack straight from the fridge so the chocolate stays firm until morning tea.

Mars Bar Slice Recipe

Recipe by Ella McKenzieCourse: DessertCuisine: AustralianDifficulty: Easy

Servings

24

servings

Prep time

15

minutes

Cooking time – stovetop melt onlyminutes

Calories

160

kcal

Total time

1

hour 

A tried-and-true mars bar slice recipe: chewy chocolate–caramel base made from melted Mars Bars, butter and golden syrup folded through crisp Rice Bubbles, finished with a smooth milk-chocolate top that slices cleanly. Perfect for school fetes, office shouts and Friday-afternoon pick-me-ups.

Ingredients

• Base

• 6 standard Mars Bars (≈ 270 g), chopped

• 90 g unsalted butter, cubed

• 2 tbsp golden syrup

• Pinch of fine sea salt

• 1 tbsp cocoa powder (optional, for deeper chocolate flavour)

• 4½ cups (≈ 135 g) Rice Bubbles (Rice Krispies)

• Topping

• 200 g milk chocolate (or half milk/half dark)

• 1–2 tsp neutral oil (sunflower or canola), or 1 tsp copha, for easy slicing

Directions

• Prep the tin. Grease a 20 × 30 cm slice tin and line with baking paper, leaving overhang for lifting.
• Melt base. In a heatproof bowl set over gently simmering water (don’t let the bowl touch the water), combine chopped Mars Bars, butter and golden syrup. Stir constantly on low heat until smooth. If a few nougat flecks remain, remove from heat and keep stirring—they’ll dissolve with residual warmth. Stir in salt and cocoa, if using.
• Fold cereal. Tip in Rice Bubbles and fold until every piece is coated. Work quickly so the mixture doesn’t set in the bowl.
• Press. Scrape mixture into the lined tin. Lay a sheet of baking paper on top and press firmly and evenly with your hands or the base of a measuring cup. Chill 15–20 minutes until just firm.
• Top. Melt chocolate with neutral oil in a clean heatproof bowl over barely simmering water (or in the microwave on 50% power in 20–30 second bursts). Stir until smooth. Pour over the base and smooth with an offset spatula.
• Set & slice. Chill 45–60 minutes until the chocolate is set to the touch. Lift out, warm a large sharp knife under hot water, dry it and cut into squares, wiping the knife between cuts.

Notes

• For extra-thick topping use up to 250 g chocolate.
  If the base is crumbly you may have added too much cereal; press firmly and drizzle a little extra melted chocolate into any gaps before topping.
• If the chocolate blooms (light streaks), it’s cosmetic only. Keep slices chilled and they’ll still taste perfect.
  Halve or double the recipe easily; adjust tin size and chilling time.

Technique Troubleshooting (Real-World Fixes)

My nougat didn’t melt.
The heat was too high or the mix overheated and seized. Take the bowl off the heat and stir firmly to use residual warmth. A teaspoon of warm milk can help smooth it out.

The base is greasy.
Too much butter, or the mix sat too long before cereal went in. Stick to the measurements and fold cereal in promptly.

The chocolate shattered when slicing.
Let the slab sit at room temp for 10 minutes, or warm the knife. Adding a teaspoon of oil to the chocolate prevents shattering next time.

Slice too soft on a hot day.
Chill longer and keep refrigerated until serving. Use a little less golden syrup (1 tbsp) in summer.

Bars won’t hold together.
Either not enough chocolate–caramel mix or too much cereal. Measure cereal lightly (don’t pack the cup) and press firmly into the tin.

Case Study: The Office Shout That Won a Promotion (Almost)

When I returned from parental leave, I wanted to bring something to the Friday stand-up that didn’t require everyone to eat off plates while juggling laptops. A double batch of this mars bar slice recipe did the trick—tidy to hold, guaranteed crowd-pleaser. My boss later confessed it was the first time the whole team stayed in the kitchen to talk about something other than sprint goals. “You can lead retros,” she said. “Anyone who can organise a slice like that can run a meeting.” I’m not saying the slice got me a promotion, but I’m also not not saying it.

Make It a Platter (Aussie Dinner Ideas: Dessert Edition)

While this is definitely not “dinner,” I often build a simple dessert board for casual BBQs: squares of Mars Bar Slice, cut fruit, pretzels, and bowls of whipped cream and strawberries. It sits happily on the table, and guests can help themselves between rounds of chatter. If you’re searching for aussie dinner ideas that end sweetly without fuss, this is it.

Frequently Asked Questions (FAQs)

Nutrition Snapshot

Per small square (1 of 24): approximately 160 calories, 7 g fat, 22 g carbohydrates, 2 g protein. Values will vary depending on brand of chocolate bars and chocolate used.

Conclusion

There are fancier desserts in the world, but few deliver the delight-per-minute of a great mars bar slice recipe. With a handful of ingredients and a saucepan, you get a slab that slices neatly, tastes like childhood, and makes people light up when they see it on the table.

This Australian mars bar slice recipe is the one I keep laminated inside my recipe binder because it never fails me fundraisers, school lunches, Friday treats, or the dessert board at a backyard BBQ.

Make a tray this weekend, then hide a square or two in the freezer for future you. You’ll thank me later.