For the dough, boil 1/8 litre of water, fat and salt. Add the flour all at once. Stir the dough in the pot on the hob until it comes off the bottom of the pot as a lump. Remove the pot from the stove. Stir in eggs one after the other. Pour the dough into a piping bag with a star-shaped spout and squirt 8 small rosettes onto a baking tray lined with baking paper. Bake in the preheated oven (electric cooker: 200 °C/ gas: level 3) for about 35 minutes.
Cut open immediately with scissors and let cool off. Drain the mandarins and collect the juice. Mix quark, crème fraîche and 3-4 tablespoons of mandarin juice. Season to taste with sweetener. Spray curd onto the lower halves of the cream puffs and cover with some mandarins. Sprinkle with pistachios