Pre-heat your oven to 140C Fan/325F/Gas Mark 3, and line a cupcake tin with cupcake cases
For the cupcake sponge, mix together the baking spread and caster sugar, ideally using an electric hand mixer or in a stand mixer with the paddle attachment, for 5 minutes until smooth and fluffy
Add the eggs, milk and vanilla extract, and mix them in well
Then gently whisk, or fold in, the self raising flour, custard powder and baking powder
Divide the mixture between the cupcake cases, and bake them for 25-30 minutes or until a thin skewer inserted in the centre of the cupcakes comes out clean. Put them on a rack to cool completely
Use a cupcake corer or a knife to make a hole in the middle of each cupcake, and fill them with the ready made custard
For the buttercream, mix the softened butter on it's own for a few minutes. Then add the icing sugar, custard powder, vanilla extract and milk, and mix until smooth. You can do this by hand, but an electric hand whisk or stand mixer with paddle attachment will provide the best results. If the buttercream is too stiff, you can add a little more milk
Spread or pipe the buttercream on top of the cupcakes, and decorate with the whole Custard Cream biscuits and the Custard Cream biscuit crumbs
Store in an airtight container in a cool place and eat within 3 days
Notes
Make sure all your ingredients (particularly the butter and eggs) are at room temperature before you start baking.
I used a baking spread for the cupcakes and unsalted butter for the buttercream.
I used ready made custard for the filling, which you can buy either in a carton or a tin, if you'd like to make your own creme patisserie for the filling, follow the instructions in my Queen Of Pudding Cupcakes recipe.
The Custard Cream biscuits will go soft after being in the buttercream for a little while, so add them as close to serving as you can.
For more information on how to bake perfect cupcakes, check out my Vanilla Cupcakes recipe!
Although I provide cup measurements, I highly recommend weighing your ingredients out using digital kitchen scales. It is the most accurate way to measure ingredients and will ensure the best results. Digital scales are very low cost and can be purchased for around £12 ($16.50).
For teaspoon (tsp) and tablespoon (tbsp) measurements, please use measuring spoons and not the type of spoons you eat with. Again this will ensure accuracy and provide the best results.