Put flour, soft fat, egg, sugar, vanillin sugar and salt in a mixing bowl. Crumble the yeast on top, warm the milk, pour in and knead everything into a smooth yeast dough. Cover in a warm place and let it rise for at least 30 minutes.
Wash the plums, dab dry, halve and stone them. Cut halves into cubes. Mix 50 g hazelnuts, sugar, plum jam, lemon peel, cinnamon and clove powder into the plums. Roll out the yeast dough on a floured work surface to a long rectangle of 60 x 24 cm.
Sprinkle with remaining hazelnuts and spread the plum filling on top. Roll up from the long side and place in a greased springform pan with breadcrumbs and a wreath insert (26 cm Ø).
Cut the wreath in serrated form with a sharp knife. Cover and leave to rise in a warm place for 15-20 minutes. Mix egg yolk and cream and spread the wreath with it. Bake in the preheated oven (electric: 200°C/ gas: level 3) for 50-60 minutes (cover halfway through the baking time).
Let the wreath cool down in the mould. Warm the jam, pass it through a sieve and coat the surface of the wreath with it. Stir icing sugar and lemon juice until smooth. Spread over the jam and sprinkle with chopped pistachios.
Whipped cream tastes good with it. Makes about 20 pieces.