Makes: 24 discs, to give 12 finished biscuits
For the biscuits
125g icing sugar
225g plain flour, plus a little more for dusting
225g unsalted butter
caster sugar, for sprinkling
For the filling
2 tablespoons custard powder
100g unsalted butter, at room temperature
150g icing sugar, sifted
2 tablespoons water, or as needed
Method Prep:45min › Cook:9min › Ready in:54min
Preheat the oven to 180 C / Gas 4. Line 2 baking trays with baking parchment. Do not grease.
Sift the 125g icing sugar, plain flour and cornflour into a large mixing bowl.
Add the butter and knead together with your hands until a pastry-like dough forms.
Take the dough out of the bowl and, on a lightly floured work surface, knead the dough a little more until it forms together in a large ball. Be careful not to over-knead as the dough will become too dry.
Roll out the dough to around 5mm thick and cut with a 5cm round biscuit cutter to create the discs. Place each disc on the tray 5cm apart.
Bake in the centre of the oven until golden brown and semi firm, about 9 minutes.
Remove the biscuits from the oven and leave them to cool completely on the tray (they will harden as they cool).
For the custard filling, mix the custard powder, butter and icing sugar in a large mixing bowl, using an electric hand mixer. Gradually add the water and continue whisking until the desired consistency is reached.
Using an icing spatula or a flat-edged knife, spread the desired amount of filling on the flat side of a biscuit and sandwich together with another biscuit.
Repeat with the remaining biscuits and dust with sifted icing sugar to finish before serving