Weet-Bix Marshmallow Slice 

If you are looking for a slice recipe that is ideal for all of the family then look no further.

And whether you call those well-known breakfast bricks, Weet-Bix, Weetabix or something completely different, the result is the same. A tasty snack treat!

This weet-bix marshmallow slice recipe is simple to make and tastes delicious. 

Various Sweets and Marshmallows. Weet-Bix Marshmallow Slice

What Do You Need?

To make this weet-bix marshmallow slice recipe you need a large, deep tray. Line this tray with parchment paper. You will need two mixing bowls – one for the base and one for the marshmallow topping.

You will need two saucepans- one to melt the butter and one to heat the ingredients for the marshmallow topping.

Ideally, you should use a cooking thermometer or sugar thermometer to check the temperature of the marshmallow topping ingredients.

Don’t have a Sugar Thermometer? Don’t worry. You can buy one here. Better still, a lots of modern Cooking Thermometers can be used for other foods as well.

You will also need an electric hand whisk. To slice it into squares you will need a sharp knife. 

If quick and easy no bake cooking is your thing, try our Hedgehog Slice.

Tips And Tricks 

If you want to ensure that your weet-bix marshmallow slice is a success then you should follow these tips and tricks. 

  • Making the base – There are a few things to remember when making the base of this slice. Make sure that the weet-bix biscuits are crushed well so that they have a fine consistency. Mix all of the dry ingredients together so they are evenly distributed before adding the butter, as once the butter is added the ingredients will begin to clump together. When melting the butter, do this gently so it doesn’t burn or brown – this would change the flavour of the base. Make sure that all of the dry ingredients are well coated in the melted butter. Press the base firmly into the tin. 
  • Baking the base – You will need to bake the base for between 10 and 15 minutes. This will depend on your oven and how efficient it is. If in doubt, check the base after 10 minutes. 

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  • Heating the marshmallow topping – When you make the marshmallow topping, you should begin by heating the ingredients very gently. The sugar and gelatine powder need to dissolve without burning. Once they have dissolved, you can increase the temperature so that the ingredients simmer. It is important that the ingredients reach a temperature of 100 degrees celsius or 212 degrees Fahrenheit. If they do not reach this temperature before cooling then the mixture might not set properly. 
  • Whipping the marshmallow – Make sure that the mixture has cooled entirely before you whip it. If you try to whip it while it is still warm to save time, it will not create the right consistency and you could end up ruining it. 
  • Setting the topping – Be patient when it comes to setting the marshmallow topping. You need to make sure that this is fully set before you attempt to cut the slice into squares. It should take about 2 hours, though it can depend on your refrigerator and the settings you use. 

Wondering what to have for dinner tonight? Why not give our Fettucine Carbonara Recipe a go?

How Can You Customise This Recipe?

There are several ways that you can customise this recipe if you want to. 

  • Weet-bix base – When it comes to the base of this slice, you could experiment with different crushed cereals to see how it impacts the texture and the flavour. You could also use crushed biscuits instead. 
  • Vanilla flavour – The marshmallow topping has a vanilla flavour, but you can switch this out for a different flavour if you prefer. You could try almond essence, lemon essence, or even raspberry essence. 
  • Food colouring – This recipe uses pink food colouring, but you can choose whatever food colouring you prefer. You may want to choose your food colouring depending on which flavour you are using. 
  • Extra ingredients – There are extra ingredients that you may choose to add. You could include a layer of fruit jam on top of the cooked base and underneath the marshmallow topping. Lemon curd would also work well. You could also add some sprinkles to the top of the marshmallow.

Weetbix Marshmallow Slice 

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Recipe by Faye Keenan Course: Recipes


Prep time


Cooking time






  • 3 3 Weetbix (crushed)

  • 1 Cup 1 Self Raising Flour

  • 1 Cup 1 Coconut (fresh chunks, refrigerated)

  • 0.75 Cup 0.75 Granulated sugar

  • 120 grams 120 Butter

  • 1 Cup 1 Water

  • 1 Cup 1 Caster sugar

  • 1 Tablespoon 1 Gelatine Powder

  • 2 Drops 2 Pink Food colouring

  • 1 Teaspoon 1 Vanilla essence


  • Start by preheating the oven to 350 degrees fahrenheit. Prepare your tray by lining it with parchment paper.
  • You begin this recipe by preparing the base. Add the crushed weetbix, the flour, the coconut and the granulated sugar into a bowl. Mix well. Melt the butter in a saucepan or in the microwave (on a medium heat for 30 seconds at a time to prevent burning). Add the melted butter to the dry ingredients in the bowl. Mix them together until they are combined and everything is coated with melted butter.
  • Press the mixture into your prepared baking tray. Make sure it is well compacted and use the back of a spoon to smooth the surface to make it even. Put the tray in the oven and bake for 10 to 15 Minutes. Remove from the oven and set the tray aside to cool.
  • Next, you need to make the marshmallow topping. Add the caster sugar, water and gelatine powder to a saucepan. Place the saucepan over a low heat. Gently heat the ingredients until the sugar and the gelatine powder have dissolved.
  • Once the sugar and gelatine powder have dissolved, increase the heat to medium. Bring the ingredients to a simmer and cook for five minutes. If possible, use a thermometer to check that the temperature has risen to 100 degrees celsius or 212 degrees fahrenheit. This will ensure that the marshmallow will set properly.
  • Let the mixture cool in the saucepan. Once it has cooled, transfer it to a bowl. Add the vanilla essence and the pink food coloring. Using an electric hand whisk, beat the mixture until it is nice and thick and forms thick peaks.
  • Spread the marshmallow mixture over the base in the tray, which should now be cool. Place the tray in the refrigerator and leave it to cool for at least 2 hours, or until it is fully set. Once it is set, you can use a sharp knife to cut the slice into squares.
Faye Keenan
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