1. Melt the butter and mix it with the lukewarm milk. The mix should have a maximum temperature of 113°F (45°C).

2. Mix flour, dry yeast, sugar, and salt in a large bowl. Add the milk-butter mixture, vanilla extract, and egg, and knead everything for 5-6 minutes until you get a smooth dough. Shape into a ball, cover the bowl, and let the dough rise in a warm place for about 45 minutes.

3. Line a small rimmed baking sheet (about 9×12 inches/23x30cm) with baking parchment. Place the risen yeast dough on the baking parchment and then either roll it out on the tray or simply pull/press it into shape until your reach the edges of the baking sheet. Prick the dough with a fork several times, cover, and let rise again for about 20 minutes.

4. Preheat the oven to 390°F (200°C). Brush the risen dough with the egg yolk and sprinkle the sugar on top. Cut the butter into small pieces and press them evenly distributed into the dough. Place the tray in the middle of the oven and bake the cake for 15-20 minutes – the top of the cake should a nice golden color, but not be overly browned. Remove from the oven and let cool down. If there are still small puddles of melted butter visible – don’t worry – they will disappear after a few minutes. If you like, you can dust the cake with some confectioners’ sugar before serving (optional)…. but there is actually enough sugar on top already ;P