Separate the egg and chill the egg white. Mix 225 g flour, 100 g sugar, 1 pinch of salt and 2 tsp cinnamon in a bowl. Add butter in pieces, egg yolk and possibly 1 tbsp. cold water. Knead first with the dough hooks of the mixer, then quickly with your hands to a smooth dough.
Cover and chill for about 1 hour.
Mix 60 g sugar and 1 tsp cinnamon. Preheat the oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Line two baking trays with baking paper. Roll out the dough in portions on a floured work surface to a thickness of 2-3 mm.
Use a cookie cutter to cut out approx. 80 hearts (approx. 6 cm Ø each), knead the dough again and again, roll out again and cut out. Spread half the hearts on the trays.
Spread the hearts on the trays with egg white and sprinkle with half of the cinnamon sugar. Bake in a hot oven for 8-10 minutes one after the other. Take out, let cool for about 5 minutes. Then remove from the baking tray together with the baking paper and let it cool down.
Spread the remaining hearts in the same way, sprinkle with cinnamon sugar and bake.