Preheat the oven to 190 ̊C/170 ̊C fan/gas mark 5. Grease a doughnut mould or a round savarin mould with some butter or oil. 

To make the sponges, in a bowl, beat together the butter and sugar until light and fluffy.

Add the eggs one at a time, beating well after each addition. Stir in the vanilla. 

Sieve in the flour and baking powder. Add the milk and fold together until just combined.

Evenly divide the mixture between the prepared moulds. Bake for 20-25 minutes or until a skewer inserted in the centre comes out clean. 

Transfer to a wire rack and allow the sponges to cool completely.

For the buttercream, in a bowl beat together the icing sugar, butter and vanilla until smooth. Stir in a few drops of the pink gel colour until you reach your desired colour. 

Once the sponges are cool, turn one sponge upside down and spread on the buttercream, before you place the other half on top, so you have a giant doughnut shape.

For the icing, in a bowl combine the icing sugar, vanilla and gradually stir in the milk or water. The icing should be slightly thick but pourable. Stir in the pink gel colour until you reach your desired colour. 

Use a large spoon, drizzle the icing over the top sponge so it runs down the sides. 

While the icing is still wet, add your sprinkles. Serve immediately or allow to set.