Roughly dice the marzipan. Sift the icing sugar into a bowl. Spread marzipan, 100 g pistachios, vanillin sugar, egg white and bitter almond flavour on top and whisk smooth with the whisks of the hand mixer. Put the dough in a cool place for about 45 minutes. Then form small croissants (approx. 3.5 cm long) from the mixture.
Press one side carefully into the remaining pistachios. Place on two baking trays lined with baking paper and bake in the preheated oven (electric oven: 125 °C/ gas: level 0-1) one after the other for 17-20 minutes. Carefully lift them off the baking tray and place them on a grid. Allow to cool down well