Put flour and salt in a bowl. Make a depression in the middle. Crumble the yeast into it. Add about 1 tablespoon of sugar and half the milk. Mix with some flour. Cover the pre-dough and let it rise in a warm place for 20-30 minutes.
Melt the fat and let it cool down. Add the remaining milk, ground almonds, sugar, vanillin sugar and lemon zest to the pre-dough. Knead everything with the dough hooks of the hand mixer and add the lukewarm fat.
Cover the yeast dough and leave to rise in a warm place for 30 minutes. Place the dough on a floured work surface and knead the nuts. Roll out the stollen dough to a rectangle about 2 cm thick and give it the typical stollen shape by folding over the long sides.
Place on a baking tray lined with baking paper and leave to rest for 10-15 minutes. Preheat oven to 225°C. After inserting the oven, switch it down (electric oven: 175°C/ gas: level 2) and bake the stollen for 50-60 minutes.
In the meantime mix chopped hazelnuts, walnuts, almonds and pistachios and roast them in a pan. Melt the butter. Brush the still warm stollen with half of the butter and sprinkle with some icing sugar.
Sprinkle roasted nuts on the stollen. Spread with the remaining butter and sprinkle with the remaining icing sugar. Let the stollen cool down.