Mars Bar Slice

Published by Amy

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A true classic amongst tray bakes! Mars Bar Slice is sickly sweet, with just the right amount of chew and crunch. Perfection.

Mars Bar Slice recipe from Baking with Granny. Rice crispes and mars bars base, with a chocolate layer.

I’ve two prominent memories from my childhood that involve Mars Bars.

Random, I know.

But being such a well-known and well-loved chocolate here in the UK, I doubt I’m the only one! And if you have never had a Mars Bar (is that even possible?!) you are missing out – but fear not, this Mars Bar Slice is the perfect introduction to a life-long chocolate bar romance.

Mars Bars and I got off to a rocky start… The first memory I have is perhaps not an actual memory, but an incident I have been reminded of my entire life – so much so that it feel likes a memory now! That would be the fateful day my sister tried to kill me, as a mere baby, by giving me a treatsize Mars Bar whilst I sat in my bouncy seat. Of course, I started to choke and it was up to Granny to resolve the situation with a wallop to my back, as well as giving my murderous 2 year old sister a good telling off!

The second memory is a slightly cheerier one. I remember my Dad (our beloved Papa!) having a Mars Bar one day when I must have been about 4 or 5 years old. I asked him to try it, loved it and at some point after that I recall being in the chippy with him where he bought me one just for myself! I still remember it being the older packaging and there must have been some sort of promo or competition on the wrapper, as it also had colourful design across it too.

What could be described as a perfected chocolate bar (aside from it’s shrinking size…) – chewy caramel, soft nougat and delicious chocolate – it’s hard to imagine how you could make it any better than it already is. But to do so is actually incredibly easy!

Melt it with some butter, mix in some rice krispies, top with chocolate and bish-bash-bosh you have the most incredible tray bake which is guaranteed to be a crowd pleaser! I give you, Mars Bar Slice!

"Absolutely Outstanding! This is an amazing recipe. I love sweet stuff and this hits the spot. I have to say… I’m addicted. I bake this around once a WEEK. Yet I still can’t get enough. It’s for both adults and children and both love It! Thank you for this wonderful recipe."
Esme

How many Mars bars do you need for Mars Bar Slice?

Well, this depends on what kind of Mars Bars you are using. And even then, whilst this information is correct at the time of last update to this recipe (2023), the size of Mars Bars could well change again.

The total amount of Mars Bars needed for Mars Bar Slice is 230g. A standard Mars Bar is currently 51g, so you’d need 4 and bit Mars Bars.

Alternatively, a multi-pack (usually 4) Mars Bar is usually around 40g each. So you’d need about 6 of them.

Of course, snack-size Mars Bars are another option, as are own-brand alternatives – which likely come in different sizes once more. So your best best is to purchase enough Mars Bars to make a little over 230g, and eat any extras that are left over!

Mars Bar Slice recipe. Classic chocolate traybake made with mars bars, rice krispies and chocolate.

Ingredients:

Butter or Margarine
Either will do and it’s personal preference to which you choose. The butter/margarine helps the Mars Bars when melting and stops them from becoming overly claggy.

Mars Bars
An essential ingredients in Mars Bar slice! Whatever size Mars Bar you use, just make sure they come to the total weight listed in the recipe.

Rice Krispies
They can be branded or store-own rice crispies, it doesn’t matter at all. They – along with the melted Mars Bars and butter/margarine – are what makes up the bulk of this Mars Bar Slice. The perfect combination of sweetness, sticky caramely-nougat and crispies crunch.

Milk Chocolate
As if the Mars Bars weren’t enough, you also want a generous layer of chocolate on top, to finish this sweet little tray bake off.

Mars Bar Slice recipe. Classic chocolate traybake made with mars bars, rice krispies and chocolate.

Mars Bar Slice

5 from 11 votes
PRINT RECIPE
Course: Dessert, Snack
Cuisine: Australian, Scottish
Prep Time: 10 minutes
Cook Time: 10 minutes
Total Time: 3 hours
Servings: 8

Ingredients

  • 115 g Butter or Margarine
  • 230 g Mars Bars ((roughly chopped))
  • 130 g of Rice Crispies
  • 250 g Milk Chocolate

Instructions

  • Line a 11x7 inch baking tray with some greaseproof paper and set aside.
  • In a large bowl, melt the butter/margarine and Mars Bars over a bain marie or in short bursts in a microwave. Use the back of a spoon/spatula to break up the nougat, as this won't melt as well - don't worry about lumps though, it won't be perfectly smooth.
  • Add the rice crispies to the melted ingredients and mix well, ensuring all are coated.
  • Tip into your prepared baking tray and push down with the back of a spoon/spatula, ensuring an even finish right into the corners.
  • Melt the milk chocolate over a bain marie or in short bursts in the microwave before spreading over the top of your rice crispy base.
  • Place into the fridge to set for at least a few hours or ideally overnight. Cut into your desired portion sizes to serve.

Notes

  • For full ingredients information and substitutions, please see the Ingredients Explanation above.
  • If using full sized Mars Bars (51g) you will need a little under five Mars Bars. If you are using multi-pack Mars Bars (usually about 40g each) you will need about 6 Mars Bars.
Tried this recipe?Tag @bakingwithgranny or use the hashtag #bakingwithgranny!
Mars Bar Slice recipe from Baking with Granny. Classic traybake recipe, made with mars bars, rice crispies and chocolate.

24 Responses

  1. 5 stars
    Since the size of mars bars have changed this recipe is spot on to fit my baking tray .I followed my mums recipe from the sixties and struggled with it recently so thanks for the new measurements

  2. 5 stars
    Hi. I’ve tried twice in the past to melt Mars Bars, with no success. I tried in a bain marie, and in a microwave. All because I had A Mars Bar slice in a lovely cafe in Scotland while on holiday last year, so thought I’d try myself. Does the butter make it easier to melt? It was just a stiff claggy lump when I tried. I can’t wait to replicate them for myself and my kids thanks. Claire

  3. 5 stars
    fantastic!!!!!!

    I would love to make traditional Scottish shortbread but I’m not sure how to knead and temperature of oven.

    I’ve made before but turned out rock hard!!!! I think I need a good recipe and good technique!

    can you please help?

  4. Hello Claire (from March ’20). You have to have a bit of patience when melting MarsBars – suggest you cut the bars into quite small pieces and I’m sure the butter will also help. Keep stirring with wooden spoon.. Hope that helps – Glynis

    1. Last? If it’s anything like my house they’ll be gone in 5 minutes! Store in airtight container if you manage to salvage any

  5. 5 stars
    Back in 1980’s I worked as a sales merchandiser for Mars UK.
    The Mars bar now is more like the size of the mini 10 pack size sold back then
    Guess they were trying to save our waistline
    Great to see that an old classic traybake is so popular again

  6. Hi I’ve tryed making this but the rice Crispies base didn’t set did I use too much syrup or not enough rice crispies please help

  7. 5 stars
    Hi I’ve tryed making this but the rice Crispies base didn’t set did I use too much syrup or not enough rice crispies please help

  8. Hi I’ve tryed making this but the rice Crispies base didn’t set did I use too much syrup or not enough rice crispies please help

  9. 5 stars
    Hi I’ve tryed making this but the rice Crispies base didn’t set did I use too much syrup or not enough rice crispies please help

  10. Absolutely Outstanding!

    This is an amazing recipe. I love sweet stuff and this hits the spot. I have to say…

    I’m addicted. I bake this around once a WEEK. Yet I still can’t get enough. It’s for both adults and children and both love It! Thank you for this wonderful recipe.

  11. Would love to try the Mars Bar Slice, so printed off the receipe, then stuck, Cups how many grams of Rice Crispies would I need? my cups are all different sizes. Of course I know cups and sticks of butter are north anmerican measurements but I cannot equate them.
    Regards
    Ronnie Best

  12. Hi Amy

    I would also like to know the grams of Rice Krispies, I have tried to look up conversions but they all seem different, anyth8ng from 30 to 40 grams per cup.

    Many thanks

  13. 5 stars
    I tried this recipe as I haven’t made them before.
    Absolutely perfect. I made a few lots as it was for a party and every one of them turned out perfectly.
    Thank you for this recipe
    Xx

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Hi! I'm Amy

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Hello, I’m Amy, the voice-behind and creator-of Baking with Granny.

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