Preheat the oven to 180C and line 2 baking sheets with paper.
Sift the flour and baking powder into a bowl.
Put the butter, peanut butter and the sugar into a large separate bowl and whisk until pale and fluffy.
Add the milk, vanilla and egg and beat until smooth.
Gradually sift in the flour mixture and beat until combined.
Drop by tablespoonfuls onto the prepared baking sheets. Using 1 or 2 fingers, press down in the middle of each one to make a shallow indent. Place 1/2 tsp of jam in each indent.
Bake for 10-12 minutes, until pale golden. Using a spatula, transfer the biscuits to a wire rack to cool before serving.