Mix flour, 50 g icing sugar and salt. Add egg and butter in flakes. Knead first with the dough hooks of the hand mixer, then with your hands to a smooth dough. Cover and chill for about 1 hour. For the filling, knead marzipan, 2 tablespoons icing sugar, pistachios and liqueur until smooth.
Roll out the dough on a work surface dusted with flour. Cut out or cut out squares (approx. 4.5 x 4.5 cm). Whisk egg yolk with milk. Spread half of the dough squares with the egg yolk milk. Place approx. 1 teaspoon of filling in the middle of each square. Place the rest of the squares on top and press down firmly at the edges. Put them on a baking tray lined with baking paper. Bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 15-20 minutes. Remove the cookies and let them cool down. Chop the chocolate and melt over a warm water bath.
Place the rest of the squares on top and press down firmly at the edges. Put them on a baking tray lined with baking paper. Bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 15-20 minutes. Remove the cookies and let them cool down. Chop the chocolate and melt over a warm water bath. Pour chocolate into a piping bag or freezer bag and cut off a small corner. Cover the cookies with thin lines on the baking tray
1 1/4 hours waiting time