Weetbix Marshmallow Slice | Cooking with Nana Ling

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

A Weetbix cut with marshmallow

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

A soft baked Weetbix cookie base is topped with sweet and fluffy marshmallows.

You can color the marshmallow topping like I did here or leave it white.

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

It’s a lovely small slice recipe that’s perfect for parties or sharing over morning tea.

Weetbix Marshmallow Slice recipe

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 mom’s collection: Lourdes Hospital Recipe Book 2nd Edition.

Lourdes Hospital is located in Dubbo, NSW Australia. Unfortunately there is no date on the book but I would say it is from the 1970’s or 80’s.

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

Ingredients for Marshmallow Weetbix Slice

To make this piece you will need:

For the base

• Weetbix (or similar wheat-based cereal)
• Brown sugar
• butter
• SR flour (or plain flour + baking powder)
• grated coconut.

For the marshmallow topping

• Sugar (giant or white)
• Water
• Gelatin (or substitute agar-agar if you prefer a vegetarian option here)
• Pink food coloring (optional)
• Streusel or coconut flakes (optional).

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

How to Make Weetbix Marshmallow Slice

make base

Start by preheating the oven to moderate (180 degrees Celsius, convection).

Grease a slicing dish (approx. 28 x 18 x 3.5 cm) and line it with baking paper. Leave excess on the sides to lift the slice out after baking.

Using your hands, mash the Weetbix in a bowl until fine and crumbly.

Place the remaining dry ingredients in the mixing bowl and stir.

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

Press the mixture into the prepared disk shape with your hands and smooth the surface with the back of a spoon.

Boil 15 minutes.

Allow to cool before adding the marshmallow topping.

Add the marshmallow topping

For the marshmallows, place the water, sugar, and gelatin in a saucepan.

Heat over low heat and stir to dissolve sugar and gelatin.

Bring to a boil and cook for 5 minutes. They should only need very low heat to cook – be careful not to overcook.

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

Add the food coloring if you choose to color the marshmallow layer and mix again until the color is even throughout the mixture.

Pour onto the cooled base and spread evenly with a plastic spatula.

Add sprinkles or coconut flakes on top of the marshmallow, if you like.

Leave to set in the fridge for about 2 hours.

Using the overhanging paper, lift the disc out of the tray. Cut the slice into squares with a sharp knife.

Recipe tips and FAQs

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

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

If you make the marshmallow topping while the crust is cooking, both should be ready at about the same time.

Once you take the base out of the oven, set your timer for half an hour. When the time is up, whip the marshmallow mixture as directed, then spread onto the cooled disc.

Q. How long does it keep?

Store the disc in an airtight container in the refrigerator for up to 5 days.

Q. Do you have any other retro slice recipes?

A lot? You might like Chinese chews, Rice Bubble Slice, Jelly Slice – or check out the entire Slice collection here.