Preheat the oven to 180°C and grease two baking trays.
Cream the butter until fluffy and gradually beat in the icing sugar until combined.
Beat in the flour and custard powder, adding a little cold water if the mixture is too stiff.
Pipe 24 stars onto the trays and bake for 10-14 minutes until pale golden-brown at the edges.
Let the biscuits cool completely on the trays.
Make the filling by beating butter, icing sugar, and custard powder until light and fluffy.
Purée the strawberries and boil with sugar and butter for four minutes to make jam.
Transfer the cooled jam into a piping bag with a small nozzle.
Pair the cooled biscuits flat-side up on a clean towel.
Pipe a ring of custard cream on half the stars, fill with jam, and top with the remaining biscuits.