Weetbix Marshmallow Slice

This Weetbix Marshmallow Slice is one from the good ol’ days, with a buttery weetbix base and a marshmallow topping that can only be described as luscious.

A Weetbix Slice with Marshmallow

This slice is the less known but sweet and pretty cousin of the popular Chocolate Weetbix Slice.

A soft baked weetbix biscuit base is topped with sweet and fluffy marshmallow.

You can colour the marshmallow topping like I’ve done here or leave it white.

You can also top it with sprinkles, coconut, shaved chocolate… or again just leave it plain.

It’s a lovely little slice recipe that’s perfect for parties or to share at a morning tea.

The recipe for Weetbix Marshmallow Slice

This recipe has been around for as long as I can remember, and I found a great version of it in this community cookbook from my mum’s collection: Lourdes Hospital Recipe Book 2nd edition.

Lourdes Hospital is in Dubbo, NSW Australia. There’s no date on the book, unfortunately, but I’d say it’s from the 1970s or 80s at a guess.

My recipe here is based on the recipe in this book.

Ingredients for Marshmallow Weetbix Slice

To make this slice, you’ll need:

For the base

• weetbix (or another similar wheat-based cereal)
• brown sugar
• butter
• SR flour (or plain/all purpose flour + baking powder)
• desiccated coconut.

For the marshmallow topping

• sugar (caster or white)
• water
• gelatine (or substitute agar agar if you prefer a vegetarian option here)
• pink food colouring (optional)
• sprinkles or flaked coconut (optional).

Quantities for the ingredients can be found in the recipe card at the end of this post.

How to make Weetbix Marshmallow Slice

Making the base

Start by pre-heating the oven to moderate (180 degrees celsius, fan-forced).

Grease a slice tin (approx 28 x 18 x 3.5 cm) and line with baking paper, leaving excess on the sides to lift out slice once cooked.

Crush the weetbix into a bowl using your hands until fine and crumbly.

Add the remaining dry ingredients to the mixing bowl and stir to combine.

Melt the butter and add to dry ingredients. Mix well.

Press mixture into the prepared slice tin with your hands, evening the top surface using the back of a spoon.

Cook for 15 minutes.

Allow to cool before adding marshmallow topping.

Adding the marshmallow topping

To make the marshmallow, place the water, sugar and gelatine into a saucepan.

Place over low heat and stir to dissolve sugar and gelatine.

Bring to the boil and boil for 5 minutes. You should only need very low heat to boil – keep an eye on this so it doesn’t boil over.

Let the mixture cool for half an hour before beating (starting on low speed and moving to high speed) for about 5 minutes or until mixture is light and fluffy.

Add the food colouring if you are opting to colour the marshmallow layer and mix again until the colour is even throughout mixture.

Pour onto top of the cooled base and use a plastic spatula to spread out evenly.

Add sprinkles or flaked coconut to the top of the marshmallow if you’d like.

Allow to set in the fridge for about 2 hours.

Lift slice from tray using the overhanging paper. Cut slice into squares using a sharp knife.

Recipe tips and FAQs

Q. How do I get the timing right when making this slice?

Both the marshmallow and base need to cool for about half an hour before adding the topping.

If you make the marshmallow topping while the base is cooking, they should be both ready around the same time.

Once you take the base out of the oven, set your timer for half an hour. When the time is up, beat the marshmallow mixture as indicated and then spread it over the cooled slice.

Q. How long will it keep?

Store slice in an airtight container in the fridge for up to 5 days.

Q. Do you have any other retro slice recipes?

Plenty? You might like Chinese Chews, Rice Bubble Slice, Jelly Slice, Custard Slice – or check out the entire slice collection here.