Roughly chop the nuts. Mix jam and nuts. Separate the egg. Mix the dough and roll out thinly on a well floured work surface. Cut out about 35 circles (6 cm Ø). Brush the edges of the cut out circles with egg white.
Place a hazelnut-sized blob in the middle with a teaspoon and fold the circles in half. Press the edges together with a fork. Place the pastry pouches on two baking trays lined with baking paper.
Bake in the preheated oven (electric oven: 200 °C/ gas: level 3) for 12-14 minutes. Whisk the egg yolk and cream and spread on the cookies approx. 2 minutes before the end of the baking time.
Remove from the oven and let it cool down on a grid. In the meantime, chop the chocolate coating and melt it in a water bath. Allow to cool a little, fill into a small freezer bag and cut off a small corner with sharp scissors.
Decorate the cookies with the chocolate coating. Let the chocolate coating dry. Makes about 35 biscuits.