Put 500 g of flour in a bowl and make a depression in the middle. Heat 1/8 l milk lukewarm, crumble yeast and dissolve in it with 1 teaspoon sugar. Pour the yeast milk into the hollow and mix it with some of the flour to the pre-dough. Cover and leave to rise in a warm place for about 20 minutes
Melt 80 g butter. Add 1/8 l milk and warm up lukewarm. Add the egg, 1 egg yolk, salt, 40 g sugar and lemon zest to the pre-dough. Knead everything smooth. Cover and leave to rise in a warm place for about 1 hour
Wash the raisins, dab dry. Melt 40 g butter over a mild heat. Knead the dough and roll out to a rectangle (approx. 30 x 50 cm) on some flour. Spread liquid butter, cinnamon and raisins on top. Roll up from the long side. Put into a greased springform pan (24 cm Ø) and form a snail. Cover and leave to rise in a warm place for about 30 minutes
Bake in a hot oven (electric oven: 175 °C/circulating air: 150 °C/gas: level 2) on the lowest shelf (gas: see oven manufacturer) for approx. 50 minutes. Cool down in the mould
Beat the must, 4 egg yolks and 100 g sugar in a hot water bath for approx. 7 minutes until white and frothy. Dust the Reinling with icing sugar and serve with foam