Mars Bar Slice is one of my earliest baking memories, and I bet if you grew up in the UK there is a good chance it was also one of the first no-bake treats you ever made.
This easy retro traybake is sweet, chewy, perfectly chocolatey and takes just minutes to put together with no oven required. Whether you are whipping up something quick for a bake sale, planning ahead for parties or just craving an old-school treat with a cuppa, Mars Bar Slice always hits the spot.
The best part? It uses only five simple supermarket ingredients and comes together with minimal fuss and hardly any washing up. It’s the kind of recipe you can make with kids, take to work, stash in the freezer for later or serve with a cup of tea when friends pop by. Pure nostalgic comfort.
Why You’ll Love This No-Bake Mars Bar Slice
- Quick and beginner-friendly – ready in under 20 minutes before chilling.
- No oven needed – ideal for warm weather or simple baking days.
- Perfectly chewy and chocolatey thanks to melted Mars Bars and a silky chocolate topping.
- Great for sharing! Take to bake sales, parties, kids’ birthdays, coffee mornings or festive gifting.
- Freezer-friendly – keep a stash ready for last-minute treats.
Ingredients at a Glance
- Mars Bars – (or Milky Way if you are based in the USA) This is my mum’s recipe, and was originally written to use 3 standard size mars bars weighing 58 grams. Annoyingly, Mars Bars have been a victim of shrinkflation, meaning that a standard bar is now 51 grams. Therefore now the 174g needed for this recipe is about 3.4 standard mars bars, or 4.5 snack size bars (38g). Consider the leftover piece Chef’s Tax…
- Golden Syrup – helps the mixture melt smoothly, binds it all together with the cereal and gives the Mars Bar Slice a nice chewy texture. If you can’t get hold of Golden Syrup, try light corn syrup, honey or agave instead.
- Butter – I like to use salted butter as it adds a nice depth of flavour to the chocolate and caramel in this recipe, but unsalted is absolutely fine.
- Crispy Rice Cereal – Rice Krispies or your favourite alternative. This recipe does also work with cornflakes for a super crunchy treat. Use gluten free or allergy friendly cereal as needed.
- Chocolate – for the topping. My choice is always milk chocolate, but dark or white chocolate work too. Or try doing a mixture and marbling the top.
How to Make It
The process is delightfully simple: melt together the Mars Bars, butter and syrup until smooth, mix in the rice cereal until it is fully coated, press into a tin and finish with melted chocolate. Chill, slice and enjoy – the hardest part is waiting for it to set.
Tips for the Best Mars Bar Slice
Use fresh crispy cereal so the base stays crunchy rather than soft.
Melt low and slow to keep the Mars Bar mixture from splitting.
Stir well as the mixture melts to get rid of lumps.
Line your tin for easy removal and tidy slices.
Score the chocolate topping before it fully sets if you want neater portions.
Chill well – at least 2 hours in the fridge, ideally overnight.
Bring to room temperature before cutting to make it easier and avoid cracking the chocolate topping.
Variations
- Salted Mars Bar Slice – a sprinkle of flaky sea salt on top cuts the sweetness beautifully.
- Add Crunch – stir crushed digestive biscuits or chopped nuts through the base.
- Festive Twist – add mini marshmallows or swap the topping for white chocolate and drizzle with dark.
- Gluten-Free – use gluten-free cereal and check your chocolate labels.
- Swap the Cereal – cornflakes can work, or try Cheerios or similar.
Serving Ideas
Mars Bar Slice is perfect with a mug of tea or coffee, but it also works well:
- wrapped in parchment with a cute bow for gifting
- served cold straight from the fridge for extra chewy texture
- packed in Tupperware to be sold at a bake sale or coffee morning (bonus points if it’s for Red Nose Day iykyk)
How to Store It
Store sliced pieces of Mars Bar crispies in an airtight container at room temperature for up to a week. If your kitchen is super warm you can store in the fridge. You can also freeze Mars Bar Slice for up to a month, just layer pieces with baking paper to stop them sticking together.
Mars Bar Slice FAQs
Can I use a different chocolate bar?
Yes! Milky Way or Snickers bars also melt well and give a slightly different flavour.
Why is my Mars Bar mixture lumpy?
It may have melted too fast. Heat everything gently over a low heat and stir constantly to keep it smooth.
How long does Mars Bar Slice need to set?
Usually around 1–2 hours in the fridge, depending on the thickness of your topping.
Can I freeze Mars Bar Slice?
Absolutely, it freezes really well. Freeze in slices separated with baking paper and thaw in the fridge before serving.
More Easy Baking:
I love a sweet treat, bonus if it’s homemade! What I don’t love is too many complicated steps and/or ingredients. Like all my recipes, these sweet treats are designed to be quick and easy, ideal for family baking.
- Malteser Slice (if you enjoyed this Mars Bar Slice you will LOVE this one)
- White Chocolate Chip Brownies
- No-bake Lemon Raspberry Tart
- Chocolate Hazelnut Cookies
I hope you like this recipe as much as I do!
Don’t forget to rate the recipe and leave a comment if you make it.
Your feedback is really important and helps me keep making recipes you love!
Mars Bar Slice
Equipment
Ingredients
- 174 grams (6.14 oz) mars bars (milky way in USA) - roughly chopped
- 2 tbsp golden syrup
- 90 grams (3.17 oz) butter
- 100 grams (3.53 oz) rice krispies - or your choice of cereal
- 200 grams (7.05 oz) milk chocolate
Instructions
- Line a 20cm square baking tin with baking paper or cling film.
- Add the mars bars, butter and syrup to a saucepan and melt over a medium to low heat. Stir frequently until melted and smooth.174 grams (6.14 oz) mars bars (milky way in USA), 2 tbsp golden syrup, 90 grams (3.17 oz) butter
- Add the rice krispies to the melted mix and stir well to combine – make sure all the cereal is completely coated.100 grams (3.53 oz) rice krispies
- Pour into the prepared tin and use a spoon or spatula to press it into the tin so the mix is compacted with a nice smooth top. Pop in the fridge.
- Melt the chocolate either by the double-boiler method or in the microwave (see notes for more details). When just melted, pour over the rice krispies base and smooth it out with a spatula or the back of a spoon, making sure it reaches each corner.200 grams (7.05 oz) milk chocolate
- Chill in the fridge until set – at least 2 hours but ideally overnight. Let it come to room temperature before slicing into 16 squares (this will make it easier to cut and also avoid cracking the chocolate top).
Notes
Nutrition
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