Preheat your oven to 180C / 350F / Gas mark 4 and prep your cupcake / muffin pan with liners and place to one side.
Beat the butter and sugar together until they are light and fluffy.
Add the eggs one at a time beating in between each addition.
Mix in the vanilla extract.
Gently fold in the flour and baking powder careful not to knock all the air out of the batter.
Spoon the batter into the cases till they are 2/3 rd's full.
Pop them in the oven and check on them after 20 minutes, if a pick comes out clean they are ready, they may need a few more minutes depending on your oven. Once baked take them out of the oven but leave them in their pans for 10 minutes.
After 10 minutes take them out and place them on a cooling rack till cold.
While they are cooling make the buttercream. Beat the butter until it is very pale in colour and very fluffy. It takes me around 5-7 minutes in my mixer.
Add half the icing sugar and beat in till fully combined. Then add in the vanilla extract and the remaining icing sugar, beat till everything is well combined. If you feel it's still a little too thick add the teaspoon of milk.
Once the cakes are cold, you need to slice a disk from the middle out of them and cut it in half. You will need a sharp smooth edged knife. So do this step yourself if you are working with kids!
Add a teaspoon of jam into the hole.
Carefully spoon the buttercream on top of the jam and spread it to cover the jam completely. With the disk cut in 2 place them in the buttercream so they look like butterflies. Dust with a sprinkle of icing sugar.
Best eaten within 3 days, but kept in an airtight till they will last up to 5. Undecorated you can freeze these cakes for up to 2 months.