Mix flour, butter in flakes, icing sugar and an egg first with the dough hook of the mixer, then with your hands to a smooth dough.
Cut the vanilla pod open lengthwise and scrape out the pulp with the back of a knife. Knead the vanilla pulp with the dough. Wrap in foil and chill for about 30 minutes.
Roll out the dough on a lightly floured work surface to a thickness of approx. 7 mm. Cut out 21 circles (each 8 cm Ø). Knead the dough again and again and roll out again. Heat the jam in a small pot and stir until smooth. Spread 14 circles with the jam. Put 2 circles of jam on top of each other. Place another circle without jam on top. Chill the dough circles for about 45 minutes.
Cut each circle of dough into 8 "cake pieces". Place the cookies on 2 baking trays lined with baking paper. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) one after the other for 10-12 minutes. Let the cookies cool down.
Chop the chocolate coating and melt it over a warm water bath. Pour into a freezer bag and cut off a small corner. Decorate cake pieces with it and let them set. Mix the egg whites and icing sugar with the whisk of a hand mixer until smooth. Fill into a freezer bag and cut off a small corner. Spray a little tuff on each "tartlet". Let the tuffs dry. Store cookies in a tin can.