ready in 1 hr 15 min.
Heat the oven to 190°C (170° fan) 375°F gas 5. Line 2 baking trays with non-stick baking paper.
Beat the butter and sugar in a mixing bowl until soft and light. Beat in the vanilla and egg.
Sift in the cornflour and both flours and stir until combined. Chill for 30 minutes.
Roll heaped teaspoons of the mixture into balls and place on the baking trays. Make a deep indentation in the centre of each ball with a wooden spoon handle dipped in flour.
Fill each indentation with 1/2 teaspoon of jam.
Bake for about 20 minutes, until pale golden. Cool on the baking trays for a few minutes, then place on a wire rack to cool completely.