Preheat the oven to 180°C, fan 160°C, gas 4.
Mix all the ingredients for the filling together in a small bowl.
Roll out the puff pastry on a floured surface to a thickness of about 3mm. Using a 10cm round cutter, cut out 12 discs.
Place 1 heaped teaspoon of the filling in the centre of each disc. Brush the edges with a little beaten egg and draw the pastry together to make a purse, squeezing tightly to seal.
Using the palm of your hand, flatten each cake until you can see the currants through the pastry. Place on a baking tray, sealed side down. Brush with more beaten egg, then sprinkle with caster sugar. Using a sharp knife, make 3 parallel cuts on top.
Bake for 20–25 minutes, until the pastry is golden. Leave to cool on a wire rack. Great served either warm or cold with a cup of tea.