Separate egg, chill egg white. Mix flour, salt, 100 g sugar and 2 tsp cinnamon in a bowl. Add butter in pieces and egg yolk. Knead first with the dough hooks of the hand mixer, then with your hands to a smooth dough. Cover the dough and chill for about 1 hour
Briefly knead the dough and roll out in portions to a thickness of approx. 2 mm on a floured work surface. Cut out hearts (approx. 6 cm Ø) and distribute on baking sheets lined with baking paper. Mix 1 tsp. cinnamon and 60 g sugar. Spread hearts with egg white and sprinkle with cinnamon sugar. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) one after the other for 8-10 minutes. Let it cool down on a cake rack
Waiting time approx. 1 hour