Pre-heat your oven to 160C Fan/180C/350F/Gas Mark 4, and grease and line two 8" cake tins that are at least 2" deep
To make the sponge, start by mixing the butter, light brown sugar and caster sugar together in a large bowl, ideally using an electric mixer
Add the eggs and milk, and whisk until fully incorporated
Add the self raising flour, cocoa powder, malt powder, bicarbonate of soda and baking powder and whisk or fold in gently
Divide the mixture between the tins, use scales for accuracy if you like
Bake them for 35-40 minutes or until a thin skewer inserted in the middle comes out clean. Leave them to fully cool either in the tins or remove from the tins and place on cooling racks
To make the buttercream mix the butter on its own for a few minutes. Add the malt powder, icing sugar, milk and vanilla extract, and mix until smooth. For best results use a stand mixer with the paddle attachment. If the buttercream is too stiff then you can add a little more milk
If the cakes have domed on top, level them off with a cake leveller or a serrated knife
Put one of the sponges on your plate or cake stand and spread half of the Maltesers spread onto it
Then pipe buttercream over the Maltesers spread
Add the second sponge and spread the remaining Maltesers spread over it, followed by more buttercream
Decorate with whole and crushed Maltesers
Serve immediately, store leftovers in an airtight container in a cool place for up to 3 days