Separate the egg. Roughly dice the marzipan. Sift icing sugar, flour, cocoa and espresso powder on top. Add the egg white and knead with the dough hooks of the hand mixer to a smooth mixture.
With moistened hands form approx. 35 balls from it. Place them on a baking tray lined with baking paper. Mix egg yolk and cream. Brush the balls with it. Press three pistachio kernels at equal intervals on each ball.
Bake in the preheated oven (electric cooker: 150 °C/ convection oven: 125 °C/ gas: see manufacturer) for 20-25 minutes. Remove from the oven, place on a cake rack and allow to cool.