250 g Plain flour
75 g Granulated sugarplus more for the top
200 g Butterchopped
2 tsp Lemon zestunwaxed and finely grated
1 Egglightly beaten
Sift the flour into a bowl and mix in the sugar, butter and lemon zest, first by rubbing with your fingers and then by mixing with a wooden spoon, until the dough is smooth and firm. Wrap in cling film and place in the refrigerator for one hour.
Preheat the oven to 190°C.
Now place the dough between two sheets of baking parchment and roll it out to a rectangle about 1.5 cm thick. Remove the top layer of baking parchment.
Brush the dough with egg and dredge sugar densely on top. Carefully roll over it with a rolling pin, so the sugar is pressed slightly into the dough to make the crisp topping to these cookies. Cut into 3 x 2 cm pieces, place them on baking trays lined with fresh sheets of baking parchment and bake for 15-18 minutes. Leave to cool on a wire rack.
When they are completely cold, store them in an airtight container. They should keep for two to three weeks.