Mix the flour with the baking powder, add the remaining ingredients and knead everything into a firm dough.
Wrapped in foil, leave to rest in the refrigerator overnight.
Roll out the dough on a lightly floured surface 0.5 cm thick, cut out small hearts, rosettes or whatever.
Place the cookies on baking sheets lined with baking paper. Garnish each with a walnut half. Possibly chill briefly. Bake in a preheated oven at 180 ° C top / bottom heat or 160 ° C fan oven for 12 - 15 minutes.