Pre-heat your oven to 160C Fan/350F/Gas Mark, and grease and line three 8 inch sandwich tins that are at least 2" deep
To make the sponge, mix together the butter and sugar until light and fluffy, around 3 minutes. Use an electric mixer for the best results
Add the eggs (I add them all at once, or you can add two or three at a time) and whisk them in
Add the lemon juice and the self raising flour and whisk or fold it in gently
Then fold in the lemon zest using a spatula, as it can get stuck in whisks
Divide the mixture between the three cake tins, I like to weigh it out using scales for accuracy, so the layers are even
Bake them for 35-40 minutes, or until a thin skewer inserted in the middle comes out clean. Then remove them from the tins carefully and let them cool completely on a cooling rack. Or you can cool them in the tins
To make the buttercream, mix the butter on it's own for a few minutes, then add the icing sugar, lemon extract and milk. For best results use an electric hand mixer or your stand mixer with the paddle attachment. If it is too stiff, add a little more milk
Stack the sponges up on your plate or cake stand, piping or spreading buttercream between each layer and drizzling the lemon curd over the buttercream
When you get to the last layer add the sprinkles and lemon jelly sweets if using
Serve immediately, store leftovers in an airtight container in a cool place and eat within 3 days