Mix the flour, dry yeast, sugar, vanilla sugar and salt.
Add lukewarm milk and an ADDITIONAL 1/8 liter of lukewarm water and work everything into a smooth dough. Cover and let rise at room temperature for about 25 minutes.
Melt 100g butter and cool slightly and mix with the egg yolk and knead this into the set dough. Don`t let go anymore.
Roll out the dough on a floured work surface into a rectangle (50x40cm).
Spread the plum jam evenly on it and spread the grated lemon zest over it.
Roll up the dough lengthways and cut into about 16 pieces. Press each snail a little flat again with your hand and place it on a baking sheet lined with baking paper and cover it for another 20 minutes.
Then bake the snails in the preheated oven at 200 ° C on the 2nd shelf from the bottom for 15 to 20 minutes until golden yellow.
Immediately after baking - STILL HOT - brush with 30g melted butter and sprinkle with cinnamon sugar.