175g unsalted butter, at room temperature
40g icing sugar, sifted
¼tsp vanilla essence
225g flour, sifted
40g custard powder, sifted
For the filling
50g butter, softened
80g icing sugar, sifted
2tbsp custard powder, sifted
Preheat oven to 180C/350F/Gas 4. Line a baking tray with baking paper.
Cream together the butter and icing sugar in an electric mixer until light and fluffy. Add the vanilla essence, the flour and custard powder and mix gently until a dough forms. Roll teaspoons of the dough into walnut-sized balls and place on the prepared tray. Flatten the top of each with a fork: this will make about 32 biscuits. Bake for 12 minutes until just golden underneath. Cool on a wire rack.
To make the filling, beat the butter, icing sugar and custard powder together in an electric mixer until smooth.
Once the biscuits are cool, place ½tsp of the filling onto the flat side of one biscuit and press the flat side of another on top to form a sandwich. Store in a sealed container until ready to use; they will keep fresh for several months.