Pre-heat your oven to 140C Fan/325F/Gas Mark 3, and line a cupcake tin with cupcake cases
To make the sponge, mix together the butter and sugar, ideally using an electric mixer, for exactly 5 minutes
Add the eggs and vanilla extract, and mix in well
Then gently whisk or fold in the self raising flour
Fold in the sprinkles with a silicone spatula or a wooden spoon until evenly distributed
Divide the mixture between the 12 cupcake cases
Bake them for 25-30 minutes or until they are golden brown and a skewer inserted in the centre comes out clean. Leave to cool completely on a cooling rack
Make the buttercream by mixing the butter on it's own for a few minutes. Add the icing sugar, vanilla extract and milk, and mix until smooth. For the best results use a stand mixer with the paddle attachment. You can add a little extra milk if it is too stiff
Pipe the buttercream onto each cupcake using a piping bag fitted with a nozzle. Or spread on with a spoon
Then add the sprinkles as decoration
Store in an airtight container in a cool place, eat leftovers within 3 days