Pre heat oven to 175c/150c fan oven/375f. Put 12 cupcake cases into a cupcake tin.
Mix together flour, baking powder and baking soda in a bowl.
Mix the wet ingredients into the dry ingredients until combined.
Divide the batter between the 12 cases and bake in the oven for 18-20 minutes until a skewer inserted into the cakes comes out clean. Leave to cool.
In the bowl of your mixer add the butter and beat for a couple of minutes until the butter is light and fluffy. Gradually add in the Icing sugar, carefully beating between each addition. Once all the icing sugar is added it will be quite stiff, add in the cocoa powder, sour cream and melted chocolate. Carefully beat this into the mixture. Beat for a further 2-3 minutes to get a light and fluffy frosting.
Cut out the centre of each cupcake and spoon in a teaspoon of blue or pink sprinkles. Put the hollowed out piece back on top of the cupcakes.
Fill a piping bag fitted with a closed star nozzle with your chocolate frosting and pipe a generous swirl onto each cupcake. Finish them off with a few multi coloured sprinkles. Enjoy!