1 Mix together the flour and ground almonds.
2 Whisk together the butter, icing sugar, caster sugar, vanilla and egg yolks until blended. Stir in the flour mixture until smooth. Wrap in cling film and chill for 1 hour.
3 Preheat the oven to 170°C(150° fan)|325F|gas 3. Line two large baking trays with greaseproof paper.
4 Knead the dough lightly on a floured surface and roll out to 1/2 cm | 1/4" thickness. Cut out rounds using a fluted cutter, and re-roll the trimmings.
5 Arrange the rounds on the baking trays and cut out small holes from the centres of half of the rounds.
6 Bake for 10-12 minutes until pale golden. Cool on the trays for 5 minutes, and then place on a wire rack to cool completely.
7 Spread the lemon curd on the rounds without holes and place the cut-out rounds on top, pressing gently. Sprinkle with caster sugar before serving.