Cut the marzipan into pieces. Mix marzipan and egg white with the whisk of the hand mixer to a smooth dough. Add sugar, salt and vanilla sugar and stir in. Sift the flour onto the marzipan-sugar mixture and stir in.
Pour the dough into a piping bag with a large perforated spout and squirt eight croissants onto a baking tray lined with baking paper. Sprinkle with almonds and press down lightly. Bake the almond croissants in a preheated oven (electric cooker: 175°C / gas: level 2) for 15 minutes until golden brown. Let them cool down on a cake rack.
Melt the couverture in a water bath at low heat. Dip each end of the croissants into the couverture and leave to dry on the cake rack.