Mars Bar Slice – or Mars Bar Traybake – is yet another one of those classic cakes you’ll see in cafes across Scotland, alongside Tiffin, Millionaire’s Shortbread, Malteser Traybake, and Mint Aero Traybake. We can’t resist a slice whenever we see one (which is far too often!).
Like many delicious traybakes found in Scotland, we decided it was about time to try our hand at making it at home.
It might have been a mistake. Only because we realised HOW EASY it is!
And that means we don’t even need to leave the house to have a delicious slice of Mars Bar Cake anymore. Oops.
But in any case, it does mean that we can share this amazingly simple Mars Bar Slice recipe with you, and you can reap the benefits along with us.
What is a Mars Bar Slice?
A Mars Bar Slice is as simple as it is delicious. We’re pretty sure you would have had one of these when you were growing up. But just in case you missed out, here’s what they are.
A Mars Bar Slice is melted Mars bars, mixed with butter and Rice Crispies. The mixture is then added to a tray, and a topping of melted chocolate can be added before popping in the fridge to cool.
We told you they were simple. You may wonder why they’re so popular. Well, on top of being super simple, they are also deliciously decadent.
The taste of the Mars Bar comes through the crunch and the snap, crackle and pop of the rice crispies.
The extra chocolate on the top seems a little overkill, but it works perfectly to finish off this underrated sweet treat.
What Else is a Mars Bar Slice Called?
While researching the wonderful Mars Bar Slice, we realised they actually have more than one name.
Across the world, the humble Mars Bar Slice is also known as:
- Mars Bar Squares
- Mars Bar Cakes
- Mars Bar Crispy Cakes
- Mars Bar Krispie Squares
- and even Mars Bar Krispie Cakes!
A slice by any other name turns out to be the same! Whatever you’ve grown up calling them, you’ll know they taste amazing.
Why Make a Mars Bar Slice?
This recipe only has four ingredients and takes just 20 minutes to make (or even less once you know what you’re doing and have made it a few times!).
Also, Mars Bars are one of our favourite chocolate bars, and they’re easy to find all over the place.
That makes this recipe a great one to make! However, you can also try something similar with some other chocolate bars too. The possibilities seem endless!
We love simple recipes with few ingredients here at Scran; just check out our Scottish Macaroons, No-Bake Malteser Traybake or our Mint Aero Traybake recipes to see what we mean!
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Things you’ll need to make Mars Bar Slice
- Large bowl
- Microwave safe bowl/jug for melting chocolate
- 20cmx20cm baking tin – we love this one because the edges aren’t too rounded and you can pop out the bottom
- Large Saucepan
Ingredients for Mars Bar Slice
Yield: 16 squares
Prep time: 20 minutes
Chilling time: 2 hours
- 5 full-size Mars Bars (51g each)
- 90g unsalted butter (1/3 cup + 1 tbsp)
- 120g Rice Krispies (4 2/3 cups)
- 300g milk chocolate (1 ¾ cups)
Optional – Golden Syrup
If your melted Mars bar and chocolate mixture seems a bit lumpy and claggy ( is that a technical term..?) then you can add a couple of tablespoons of golden syrup to the mixture as well.
How to make Mars Bar Slice – Step by Step Method
Grease and line a 20x20cm square tin with baking paper. This makes it easier to pull out after, or you can use a loose bottom tin like the one we have.
Chop the Mars Bars into chunks approx. 1cm thick.
Add the chopped Mars Bars and the butter to a large saucepan and heat on the low-medium temperate, stirring frequently until mostly melted.
The nougat section of the Mars Bars will not melt completely but that’s ok!
Pour the Rice Krispies into the saucepan and stir well until completely coated in the Mars Bar mixture.
Spoon the mixture into the prepared tin and smooth it out into an even, compacted layer with the back of a spoon.
Melt the chocolate in the microwave in 30-second bursts, stirring in between.
Pour the melted chocolate on top of the Rice Krispie layer and smooth it out to the edges. If you want you can decorate the top with chopped mars bars, but we find it’s sweet enough!
Place the tin in the fridge for at least 2 hours or overnight.
Let the traybake come to room temperature again before slicing to prevent the chocolate layer from cracking when you slice it.
Slice into 16 squares and enjoy!
Variations
If you’re wondering if this would work with other chocolate bars, the truth is we haven’t tested any to see.
However, we imagine as long as there’s a mix of chocolate, caramel, and some sort of nougat, it would likely work. We plan on trying Snickers Bars and Milky Ways next!
Frequent Questions
How long does Mars Bar Slice last?
Mars Bar Slice will last for up to a week in the fridge, but we highly doubt it’ll make it that long!
Can you freeze Mars Bar Slice?
Yes! It can be frozen in an airtight container for a month and then defrosted in the fridge for an hour or so when you want to eat it.
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What happens if the Mars Bar Slice is crumbly?
The slice should be pretty solid and easy to cut without crumbling. If it does crumble, it’s likely because the ingredients didn’t mix together enough, and it wasn’t pressed into the tin firmly enough to get rid of any air pockets.
If this happens, we just like to eat it with a spoon or sprinkle it on ice cream!
Can you melt the Mars Bars in the microwave?
Yes, you could do the butter and Mars Bar mixture in the microwave. Just make sure to do it in small bursts and stir frequently, as you would when melting any chocolate.
We find putting it in a pan and stirring easier so we don’t have to keep stopping and checking it, but you can basically make the whole thing in the microwave if you need to!
Do I need to add Golden Syrup?
Some recipes call for adding Golden Syrup (or Corn Syrup in the USA) but we’ve found it works perfectly well without it.
If you’re having trouble though with melting the butter and Mars Bars and they seem a bit claggy and lumpy, you can try and add about two tablespoons of Golden Syrup to give the extra liquid but also stickiness.
How do I cut through the chocolate layer without it cracking?
Take the Mars Bar Slice out of the fridge for about half an hour before slicing.
You can also dip your knife in hot water and dry it between slices.
Another tip is to add a teaspoon or so of coconut or vegetable oil to the chocolate when melting it to allow it to be sliced more easily, as it won’t harden so much.
When cutting, press down through the chocolate layer and then the Rice Krispies.
You can also use a small serrated knife rather than a large flat-edged one.
So whether you call them Mars Bar Slices, Mars Bar Squares, Mars Bar Cake, Mars Bar Crispy Cake, Mars Bar Krispie Squares or Mars Bar Krispie Cakes, we hope you love this recipe as much as we do and that it takes you down a chocolaty trip down memory lane!
Enjoy,
Phil and Sonja
Other Popular Traybake Recipes
- Chocolate Tiffin
- Sticky Toffee Pudding Traybake
- Mint Aero Traybake
- Old School Cake
- Almond Slice
- Millionaires Shortbread
- Fruity Flapjacks
- Jam Flapjacks
- Kinder Bueno Brownie
Yield: 16
Mars Bar Slice - A Super Easy Traybake Recipe
Mars Bar Slice - or Mars Bar Traybake - is yet another one of those classic cakes you’ll see in cafes across Scotland. We can’t resist a slice whenever we see one (which is far too often!) so we decided to make our own.
Mars Bar Slice is just two layers. One is melted Mars Bars mixed with Rice Krispies and butter, and the other is a layer of chocolate on top. That’s it. It’s that easy.
Prep Time 20 minutes
Chilling Time 2 hours
Total Time 2 hours 20 minutes
Ingredients
- 5 full size Mars Bars (51g each)
- 90g unsalted butter (1/3 cup + 1 tbsp)
- 120g Rice Krispies (4 2/3 cups)
- 300g milk chocolate (1 ¾ cups)
Instructions
- Grease and line a 20x20cm square tin with baking paper.
- Chop the Mars Bars into chunks approx. 1cm thick.
- Add the chopped Mars Bars and the butter to a large saucepan and heat on the low-medium temperate, stirring frequently until mostly melted. The nougat section of the Mars Bars will not melt completely but that’s ok!
- Pour the Rice Krispies into the saucepan and stir well until completely coated in the Mars Bar mixture.
- Spoon the mixture into the prepared tin and smooth it out into an even, compacted layer with the back of a spoon.
- Melt the chocolate in the microwave in 30-second bursts, stirring in between.
- Pour the melted chocolate on top of the Rice Krispie layer and smooth it out to the edges.
- Place the tin in the fridge for at least 2 hours or overnight.
- Let the traybake come to room temperature again before slicing to prevent the chocolate layer from cracking when you slice it.
- Slice into 16 squares and enjoy!
Notes
Do I need to add Golden Syrup?
Some recipes call for adding Golden Syrup (or Corn Syrup in the USA) but we’ve found it works perfectly well without it. If you’re having trouble though with melting the butter and Mars Bars and they seem a bit claggy and lumpy you can try and add about 2 tablespoons of Golden Syrup to give the extra liquid but also stickiness.
