Mix currants with 2 tbsp caster sugar, cardamom powder and lemon zest
In a stand mixer combine flour, baking powder, pinch salt and butter and mix until breadcrumb stage
Add 50g sugar to the mixer
Mix egg yolk with 1 tbsp milk and add to the mixer
Add milk in stages until dough starts clumping (approximately 2 tbsp total)
Stop and press dough together well
Split dough in half and roll out to 3-4mm thickness on a baking sheet
Lightly whisk egg white and brush over the first dough layer
Sprinkle currant mixture evenly over the dough
Roll out second half of dough, brush with egg white and place on top of currants
Press well together with hands or baking tray
Use a cake decorating tool to divide into rectangular biscuit shapes
Brush all over with egg white
Bake in preheated oven at 180°C for 12-15 minutes until golden brown
Cool and break into biscuits
