Knead 350 g flour, butter in pieces and sour cream first with the dough hooks of the mixer, then with your hands briefly to a smooth dough. Cover and chill for about 2 hours.
Chop the walnuts. Finely dice apricots and dates. Mix with nuts and calvados. Preheat the oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer) and line two baking trays with baking paper.
Halve the dough and chill one half again. Roll out the other half on some flour about 3 mm thin. Cut out approx. 35 circles (each approx. 7 cm Ø). Put approx. 1 tsp. of filling on each half of the circle.
Fold the other half over and press the edges together well. Roll out the rest of the dough in the same way and fill.
Spread out on the sheets. Bake one after the other in a hot oven for about 20 minutes. Remove from the oven and leave to cool for about 5 minutes. Then remove from the tray together with the paper. Let it cool down.
Mix icing sugar and lemon juice to the icing. Put them into a freezer bag, cut off one corner. Pour the icing in strips over the cookies. Sprinkle with sugar and let dry.