Pre-heat your oven to 160C Fan/350F/Gas Mark 4, and grease and line two 8" cake tins (that are at least 2" deep)
Make the sponge by mixing the baking spread and light brown soft sugar together in a mixing bowl until fluffy (around 3 minutes), ideally using an electric mixer. Or mix in a stand mixer with the paddle attachment
Add the eggs and milk, and mix until fully incorporated
Add the self raising flour, cocoa powder, 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 it's own until it's smooth and creamy, for 2-3 minutes. Use an electric whisk or stand mixer with the paddle attachment for best results
Add the icing sugar, golden syrup, milk and vanilla extract. Mix until smooth. 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 sharp knife
Put one of the sponges on your plate or cake stand and pipe or spread some of the buttercream onto it. Then sprinkle over some crushed up Crunchie bar
Add the other sponge on top and pipe or spread the remaining buttercream on top
Decorate with the Crunchie bars, chop some into chunks and crush up the rest. Leftovers will keep in an airtight container in a cool place for 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 cake and unsalted butter for the buttercream.
You can use any cocoa powder for this cake, of course the better quality it is, the better flavour it will have. Also do make sure you are using cocoa powder and not a hot chocolate powder.
I used golden syrup for the buttercream, you could use honey instead if you prefer.
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.