Place the flour, cornstarch, powdered sugar, vanilla sugar, salt and lemon zest on the worktop, make a well in the middle and let the egg white slide into it. Put cold butter in flakes on top and knead everything quickly to a smooth dough, shape into a ball and wrap in foil and put in the refrigerator for 60 minutes.
Preheat the oven to 180 ° C top / bottom heat.
Knead part of the dough until soft, roll out on a floured work surface and cut out.
Bake on a baking sheet lined with baking paper on the middle rack for about 10 minutes (depending on the size and thickness of the cookies). For me, 7 minutes is enough because I make very small cookies. Let cool down.
Do the same with the rest of the dough.
Finely dice the lemon peel. Mix powdered sugar with lemon juice to a glaze, glaze half of the cookies and decorate with a lemon cube. Let dry.
Brush the unglazed cookies with a little lemon curd and put a glazed cookie on each as a lid.