WHAT YOU NEED

For the biscuit

1 cup (250g) unsalted butter, at room temperature
80g (2 ¾ oz) icing (confectioners’) sugar
Zest of 1 orange
1tsp vanilla paste
1/3 cup (50g) custard powder
1 2/3 cups (250g) plain
(all-purpose) flour
A pinch of salt

For the filling

100g (3 ½ oz) butter, softened
2 cups (250g) icing (confectioners’) sugar
3 tbsp rhubarb or plum jam
1 tbsp orange juice, plus extra if needed

Place the butter and sugar in the bowl of a stand mixer fitted with the paddle attachment and cream for a few minutes until pale and fluffy. Or you can use a large bowl and an electric mixer.
Add the zest and vanilla and beat again. Fold in the custard powder, flour and salt. Turn the dough out onto your benchtop and divide in two, then form each half into a sausage shape. Wrap in plastic wrap and refrigerate for at least 30 minutes.

Preheat the oven to 170°C (325°F) and line two baking trays with baking paper.

Slice each sausage of dough into discs around 1 cm (½ inch) thick, and roll these into small balls. Place these on the baking trays, leaving a few centimetres (about 1 inch) between each to allow for spreading. Gently press down with the tines of a fork to flatten a little.

Bake for 15 minutes, or until pale golden. Remove from the oven and leave to cool on a wire rack.

Meanwhile, clean the mixing bowl ready to make the filling. Combine the butter and sugar in the bowl of your stand mixer, or using a bowl and an electric mixer, and beat for a few minutes until pale and creamy. Add the jam and the 1 tablespoon of orange juice and mix again until you have a thick paste. Add more orange juice if needed, a little at a time, until you have the right consistency.

Sandwich two biscuits together with a little of the filling and place in the fridge for the buttercream filling to set, then store in an airtight container for up to 2 days.