1. Start with the custard – add milk, sugar, and vanilla extract to a small saucepan. Bring to a boil over medium heat while stirring constantly, then add the semolina and let simmer for about 2 minutes. The mixture should thicken nicely. Remove from the heat and place a piece of plastic wrap on top to prevent skin from forming. Let cool down completely.

2. As soon as the custard has cooled, clean the rhubarb and cut it into small pieces. Mix in a bowl with the sugar, cover, and let it sit in the fridge for at least 10 minutes.

3. Preheat the oven to 375°F (190°C). Line two baking sheets with baking parchment and set aside.

4. Add flour, sugar, and butter for the streusels to a bowl and mix until you get different-sized streusels. Place in the fridge until ready to use.

5. For the dough, mix quark, oil, egg, and sugar in a large bowl until well combined. Mix the flour with baking powder, and salt and add to the bowl – mix in and knead until you get a nice and smooth dough. Divide into 8 equal portions, shape them into balls, and then pull/stretch each dough ball into a round disc with a diameter of about 6 inches (15 cm). The sides of the discs should be a bit thicker than the center. Place the discs on the baking sheets, spacing them slightly apart. Spread semolina pudding on each disc (leaving the edges bare) and top with the rhubarb. Brush the edges with a bit of milk and sprinkle everything with the crumbles and some additional coarse sugar.

6. Bake the streuseltaler for about 18-20 minutes. The edges and the streusel should have gotten some color. I always bake only one baking sheet at a time. You can also place both trays in the oven at once and switch their positions halfway through the baking time so all the pastries bake evenly. Remove the finished streuseltaler from the oven and let cool down completely on a wire rack.