This mars bar slice recipe melts Mars Bars, butter and golden syrup together, folds them through Rice Bubbles, and finishes it all with a smooth chocolate top. It’s chewy, chocolatey and needs no oven.
It’s a classic for bake sales, lunchboxes and birthday parties. You can make it the day before, and it cuts into neat little squares that are easy to share.
The secret is gentle heat. Melt the bars slowly so the nougat stays smooth, and add a little oil to the chocolate so it doesn’t crack when you slice it.
Table of Contents
Mars bar slice recipe at a glance
| Tin | 20 x 30 cm slice tin, lined with baking paper |
| Hands-on time | About 15 minutes |
| Chill time | 15 to 20 minutes for the base, then 45 to 60 minutes once topped |
| Makes | 24 small squares |
| Keeps | 1 week in the fridge, 2 months in the freezer |
In Australia we call these tray bakes slices. Elsewhere they’re known as bar cookies or traybakes.
Why this mars bar slice recipe works
- Low heat: melting the bars over a pot of simmering water keeps the nougat silky, not stiff.
- Quick fold: the cereal goes in straight away, before the mix starts to set in the bowl.
- Firm press: pressing through baking paper packs the base tight so it holds together.
- Oil in the chocolate: just 1 to 2 teaspoons stops the top shattering.
- A pinch of salt: it balances the sweetness and brings out the caramel.
Mars Bar Slice Recipe
Course: DessertCuisine: AustralianDifficulty: Easy24
servings15
minutes160
kcal1
hourA no-bake mars bar slice with a chewy base of melted Mars Bars, butter and golden syrup folded through Rice Bubbles, finished with a smooth chocolate top that slices cleanly.
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
- Thicker top: use up to 250 g chocolate.
- Crumbly base: you may have added too much cereal. Press firmly and drizzle a little extra melted chocolate into any gaps before topping.
- Chocolate bloom: light streaks are only cosmetic. Keep the slice chilled and it will still taste great.
- Halve or double: the recipe scales easily. Adjust the tin size and chilling time.
Mars bar slice troubleshooting
The nougat went stiff and lumpy.
The heat was too high. Take the bowl off the heat and keep stirring firmly. A teaspoon of warm milk can help smooth it out.
The base is greasy.
Too much butter, or the mix sat too long before the cereal went in. Stick to the amounts and fold the cereal in straight away.
The base won’t hold together.
Too much cereal for the melted mix. Measure the Rice Bubbles lightly without packing the cup, and press the base down firmly.
The chocolate cracked when slicing.
Let the slab sit at room temperature for 10 minutes and use a warm knife. Next time, add the oil to the chocolate.
It’s too soft on a hot day.
Chill it longer and keep it in the fridge until serving. In summer you can cut the golden syrup to 1 tablespoon.
Mix it up
| Version | What to change |
|---|---|
| Salted peanut | Add 1/2 cup roasted peanuts to the base and sprinkle flaky salt on the chocolate. |
| Milo | Stir 2 tablespoons Milo into the melted Mars Bar mix. |
| Double choc | Swap half the Rice Bubbles for Coco Pops and use dark chocolate on top. |
| Coconut | Fold 1/2 cup desiccated coconut into the base and use a little less cereal. |
| Party | Press mini marshmallows or sprinkles into the chocolate while it’s still soft. |
| Gluten free | Use a gluten free puffed rice cereal and check your chocolate labels. |
Hot weather and transport
Mars bar slice softens quickly in the heat. Keep it in the fridge until you leave, and carry it in a cooler bag with an ice brick.
For lunchboxes, pack it straight from the fridge so the chocolate stays firm until morning tea.
Make ahead and storage
Make it up to 3 days ahead and keep it chilled. Slice it on the day you serve it for the cleanest edges.
It keeps in an airtight container in the fridge for up to 1 week. To freeze, layer the squares with baking paper and freeze for up to 2 months. Thaw at room temperature for 20 to 30 minutes.
Recipes you might like
Frequently asked questions
Can I use honey instead of golden syrup in mars bar slice?
Yes. The flavour will change a little and the base may be slightly firmer. Maple syrup is too thin, so stick to honey.
Why did my Mars Bars go stiff when melting?
The heat was too high. Melt them slowly over simmering water, and if they tighten up, take the bowl off the heat and stir in a teaspoon of warm milk.
Can I use Coco Pops instead of Rice Bubbles?
Yes. Swap up to half the Rice Bubbles for Coco Pops for a more chocolatey base.
Is this mars bar slice recipe nut free?
There are no nuts in the recipe. Check the labels on your Mars Bars and chocolate for allergy warnings before taking it to school.
How far ahead can I make mars bar slice?
Up to 3 days ahead. Keep it chilled and slice it on the day for the neatest squares.
This mars bar slice recipe is quick, cheap and always popular. Melt gently, press firmly and add that little bit of oil to the chocolate, and you’ll get tidy squares every time.
Happy slicing,
Ella x
