Add the butter and sugar to a large mixing bowl and whisk together using a hand blender or food processor. It will become lighter in colour and turn almost fluffy.
300 g unsalted butter, 300 g caster sugar
Add 1/3rd of the whisked eggs together with the pinch of salt to the sugar and butter mixture and whisk again.
1 pinch salt
Add 1/3rd of the flour and whisk until combined.
300 g self raising flour
Add the remaining eggs and whisk and then the remaining flour. If using a processor, turn to low and leave until fully combined. If using a hand blender then continue until combined and now flour is visible.
Place the cupcake holders into muffin trays. This quantity will require 3 trays of 12 cakes. Fill each of the holders about ½ full and place in the oven for 25 minutes. Test they are cooked by pushing a skewer in and pulling it out. If the skewer is clean then they are cooked. If sticky then leave for a few minutes and test again.
When cooked, remove the cakes from the tray and place on a wire rack to cool.
Add the cream to a blender and whisk until you achieve firm peaks. You can place the cream into an icing bag (or place into a sandwich bag and using a sharp knife slice the corner off for a makeshift piping bag), or using a small palette knife to insert the cream.
8 oz double cream
Use a small sharp knife to cut a circle of cake out of the top of each cupcake leaving a small border and a hole no more than 1/3 inch deep. This is where the fillings will go.
Cut the removed cake circle in half to make the butterfly wings which will go back on top.
Add a little spoon of good quality strawberry jam into the well and add a squeeze of the whipped cream.
Return the pieces of cake you cut in half back onto the top and hey presto a butterfly cake.
Notes
I would sieve the flour before using just to make sure there are no large lumps.Also if the cakes are to be left out for any period of time, I would recommend using buttercream filling instead of whipped cream as it wont lose it appeal.