How to cook
Sift the flour. To it add the softened butter. Knead the 2 products until they turn to crumbs. Add the egg yolks 1 by 1, the lemon zest and juice, ground walnuts, the lemon, vanilla and rum essences.
Knead a smooth dough, wrap it in plastic wrap and leave it for about 2 hours in the fridge. Roll it out into a thin sheet onto a floured counter. Cut out circles using a glass.
Cut out shapes in half the circles - stars, hearts, Christmas trees or just holes. Bake in a preheated 356°F (180 °C) oven until they turn pink at the edges. Once cooled, sprinkle the halves you cut out shapes in with powdered sugar.
Stick them together in pairs, 1 whole and 1 cut, with jam.
The sweets turn out even better when they're lift to sit a bit. That way they take in the jam and soften.