Sift the flour and icing sugar into a large bowl. Add the vanilla, lemon zest and a pinch of salt. Rub the butter into the dry mixture using your fingertips until it resembles damp sand, then mix in the egg yolks. Knead everything into a smooth dough. Wrap and chill for at least 1 hr or up to two days.

Remove the dough from the fridge and leave at room temperature for 10 mins. Roll the dough into a long sausage shape and cut into 50 equal portions. Roll each portion into a ball and put on a baking sheet lined with baking parchment (you’ll need two or more baking sheets). Using a wooden spoon or your thumb, make an indent in each ball.

Heat the oven to 200C/180C fan/gas 6. Fill the indents with 1/2 tsp lemon curd each. Bake for 12-15 mins, then leave to cool completely on a wire rack. Dust the cookies with icing sugar and serve. Will keep in an airtight container for a week.