Cream the butter and sugar together, then add in egg, milk and vanilla extract. Mix well. 

Sift in flour and baking powder, mix well. You can add some chocolate sprinkles. 

Put the ice-cream cone in muffin tins, put the batter into double lock bag, pour the batter into the cone, half way through. Pop in preheated 180C oven, bake for 15-17 minutes or until fully cooked. 

For the buttercream : Cream the butter until light and fluffy, for few minutes. Then sift in icing powder, mix well. Add one to two tablespoons of milk, mix well. 

Add buttercream in a double lock bag with piping tip. Pipe the swirl on completely cooled cake, add some sprinkles, enjoy!