If you’re looking for the best Mars Bar slice recipe, then look no further. I love how this slice has the perfect combination of chewy and crisp, chocolate and caramel and chunks of Mars Bar to boot.

  • It’s chocolate, caramel and totally addictive in the best way.
  • The texture is all at once chewy and crisp.
  • So easy to make – just 15 minutes of effort.
  • Great for parties, picnics, potlucks and even gifting.

A favourite in many parts of the world, you may know Mars Bar slice as Mars Bar traybake or Mars Bar crispy cakes. They’re essentially Mars Bars melted down and mixed through rice bubbles (or rice krispies) , topped with a layer of chocolate, then left to set to chewy deliciousness.

If you love this, you’ll also love these no bake snickers crispy cakes! Or try these amazing chocolate cornflake cakes .

Top down view of the edge of piece of mars bar slice.

Mars Bar slice ingredients

Ingredients for Mars Bar slice on a baking tray.

Detailed quantities and instructions in the recipe card below.

  • Mars Bars: That classic chocolate candy bar filled with chocolate nougat and caramel is so good on it’s own but so good added to rice bubbles too. Moro bars work too and if you’re in the US, your version of Mars Bar is actually a Milky Way.
  • Rice bubbles: Known in some places as rice krispies, rice bubbles are little puffed bubbles of rice sold as a breakfast cereal.
  • Butter: Some unsalted butter here takes them to another level.
  • Chocolate: Just like my rocky road, the secret to the best Mars Bar slice is a combination of chocolates in the topping. Mostly milk but just a little dark are so good here.
  • Salt and Vanilla: Just a touch of salt (so good with both chocolate and caramel) and some pure vanilla extract give epic flavour.

Shrinkflation is real. Mars Bars over the years have reduced so much in size while remaining the same or increasing in price. A Mars Bar that was 53 grams just 4 years ago is now 47g. Eeeek! All that to say, check the weights on the packaging and make sure to measure by weight so you have enough.

How to make Mars Bar slice (step-by-step)

A collage showing how to make mars bar slice.

Detailed quantities and instructions in the recipe card below.

  1. Melt the Mars Bars and butter: Melt together the Mars Bars and butter in a saucepan over low heat until there is just a few lumps left. Add the salt and vanilla and stir together.
  2. Combine: Combine the Mars Bar mixture with the rice bubbles in a large mixing bowl. Mix it all up until fully combined.
  3. Assemble: Press the mixture into a square baking tin making sure to get the top nice and flat. Melt chocolate and pour it over the top. I like to marble the milk chocolate with some dark chocolate for both aesthetics and flavour.

Tips and tricks

Here’s the tips you need to make your easy Mars Bar slice the BEST EVER!

  • Weigh your bars: Due to shrinkflation (aka product size reducing while the price stays the same or rises) Mars Bars have changed over the years and will likely continue to do so. To make sure you have the perfect amount of Mars Bar (gooey delciousness) use the weight when deciding how many you need.
  • Add some extra chunks: One the great parts of Mars Bar slice is the small chunks of nougat and caramel that remain throughout. Make sure to keep a handful of chopped up Mars Bar to mix in.
  • Press the mix in firmly: When pressing the mixture into the tin, you want to press down quite firmly and try to get a flat top. This helps the slice hold together and also helps the chocolate stay on top as opposed to seeping down through any cracks.
  • Fresh rice bubbles! You must use fresh rice bubbles for the perfect amount of crunch.
  • Cutting clean slices: To cut nice clean slices, take the slice out of the fridge about 10 minutes before slicing and use a sharp knife. As an extra tip to get them perfect, clean and heat the blade of the knife before each cut. You can do that with hot water (just make sure to dry it off before cutting), with a kitchen blowtorch for a few seconds or over a gas burner for a few seconds. Be careful doing this.
Top down view of a batch of mars bar squares.


What are other names for Mars Bar slice?

Mars Bar slice is known in different parts of the world by different names, Mars Bar traybake, Mars Bar squares and Mars Bar crispy cakes being some of them.

Can you freeze Mars Bar slice?

Yes, you can freeze Mars Bar slice. Keep it stored in the freezer in an airtight container for up to 2 months.

Why is my Mars Bar slice so hard?

Mars Bar slice will be firm straight from the fridge – let it sit at room temperature for 10-15 minutes. If it’s still hard, the next question is did you use the correct amount of Mars Bar? Make sure to go by weight.

Can Mars Bars be melted?

Yes, Mars Bars melt well and will completely melt – even the nougat part. Make sure to keep it on low heat and keep stirring it.

Who invented Mars Bar slice?

A genius! Aka I have no idea who invented Mars Bar slice but it was Forrest Mars Sr in 1932 we have to thank for our much loved Mars Bar.

Is a Mars Bar the same as a Milky Way?

Yes and no! Outside of the US, a milky way is a simple choc malt nougat coated in chocolate while Mars Bar is a firmer nougat with a layer of caramel on top. In the US, however, Milky Way is what a Mars Bar is to the rest of us – nougat and caramel coated in chocolate.

Can you make Mars Bar slice with Coco Pops?

Yes, you can make Mars Bar slice using Coco Pops. It is harder to see when all the Coco Pops are coated so mix well and check as best you can.

Yield and storage

This easy mars bar slice should be stored in the fridge in an airtight container for up to a week.

To freeze it, cut into squares first, then freeze in an airtight container for up to 2 months. Thaw the squares in the fridge in about an hour.

The underside of mars bar slice.

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The underside of mars bar slice.
5 from 2 ratings
This no bake Mars Bar slice is so quick and easy with just 6 ingredients. Gooey, chewy caramel, chocolate and rice bubbles mixed together then covered in chocolate.


  • 260 g mars bars (5-6 bars, check packaging)(9.2oz) (notes 1)
  • 75 g unsalted butter (⅓ cup / 2.7oz)
  • 1 teaspoon vanilla extract
  • ¼ teaspoon table salt
  • 3 ½ cups rice bubbles (rice krispies) (100g / 3.5oz)
  • 250 g milk chocolate, roughly chopped (8.8oz)
  • 50 g dark chocolate, optional (1.8oz)

For best results, always weigh ingredients where a weight is provided


  • medium saucepan
  • wooden spoon / metal spoon
  • large mixng bowl
  • 9 inch square pan


  • Line an 8 or 9 inch square baking tin with baking paper and set aside.
  • Roughly chop up the mars bars. Put about 50g (1.8oz) aside (or a good handful) and add the rest to a medium saucepan with the butter.
  • On the stovetop over low heat, stir almost constantly to melt and combine together, stirring with a wooden spoon. Stop when there are just a few small lumps left.
  • Remove from heat and add the vanilla and salt and stir to combine.
  • Place the rice bubbles in a large heatproof bowl and add the rest of the chopped mars bars pieces you set aside earlier. Separate them up so they don’t all get stuck in one spot.
  • Pour over the melted butter and melted mars bar mixture and mix well with a spatula.
  • Tip the mixture into the tin and press down firmly with the back of a metal spoon or spatula all over. If cool enough you can use your hands. Try to get a fairly flat top, ready for the chocolate layer.
  • Place the milk chocolate and dark chocolate in separate microwave-safe bowls and melt in the microwave in 20-second bursts, stirring really well between each. This should only take 90 seconds. No longer or you risk burning it.
  • Pour the milk chocolate over the mars bar slice and level it out (I like using an offset spatula for this). Drizzle the dark chocolate over the top, then drag a skewer through it to marble the surface.
  • Let it set in the fridge for 3 hours before cutting into small pieces and serving.
  • Please take a moment to leave a comment & rating. It's appreciated and so helpful.


  1. Shrinkflation: I’ve used the total weight of mars bars in this recipe – due to shrinkflation, I can’t say just 5 or 6 mars bars. Shrinkflation is where a brand reduces the quantity or weight of a well-known item without changing the packaging or price. Just a few years ago, Mars Bars were 53g each; before that, they were 60g. Hence you need 260g of mars bars.
  2. Mars Bar vs Milky Ways: If you’re in the US, use Milky Ways which are almost equivalent to Mars Bars outside of the US.
  3. This recipe doubles well. Use a slice tin or 9×13 tin if doubling the recipe.

More Information

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Have you tried this recipe?Don’t forget to leave a rating and comment below and let me know how it was! I love hearing from you. Nutrition information is approximate and derived from an online calculator. The brands you use may cause variations.
Nutrition Facts
Mars Bar Slice
Amount Per Serving
Calories 229 Calories from Fat 126
% Daily Value*
Fat 14g22%
Saturated Fat 8g50%
Trans Fat 0.2g
Polyunsaturated Fat 0.4g
Monounsaturated Fat 3g
Cholesterol 10mg3%
Sodium 94mg4%
Potassium 77mg2%
Carbohydrates 28g9%
Fiber 1g4%
Sugar 19g21%
Protein 2g4%
Vitamin A 526IU11%
Vitamin C 4mg5%
Calcium 8mg1%
Iron 3mg17%
* Percent Daily Values are based on a 2000 calorie diet.