Whisk together the yeast, lukewarm milk, sugar, and flour until combined. Dust with flour, cover, and let rise for 15 minutes in a warm place without drafts.
Add all the main dough ingredients and mix with a food processor on high speed for 10 minutes, until the dough no longer sticks to the bowl, is smooth and shiny, and bubbles up. Dust with flour again, cover the bowl with a cloth, and let rise in a warm place for 1 hour, until the volume increases by at least half.
While the dough rises, prepare your chosen filling.
For quark filling: Wash the raisins in a sieve under hot water and soak in rum in a covered cup for 30 minutes, then drain.
Mix the egg yolks with sugar and add vanilla sugar. Stir in the quark, drained raisins, and lemon zest.
For powidl filling: Stir the powidl (plum jam) with rum and a pinch of cinnamon until smooth, or omit the rum if preferred.
Grease a large baking dish with 1/3 of the liquid butter.
Divide the dough into 20 pieces. Flatten each piece by hand or with a rolling pin into a small square. Place roughly 1 teaspoon of filling in the center of each square, using either quark or powidl.
Fold the 4 corners of each square to meet in the center and pinch together to seal. Place each buchtel seam-side down in the baking dish, spacing them with room to rise.
Brush each buchtel with butter as you place it in the dish.
Let rise for 15 minutes.
Bake in a preheated oven at 180°C (350°F) on the middle rack for 35 minutes until light golden.
Cool the buchtels in the baking dish, then separate them carefully. Sprinkle with powdered sugar and serve fresh.
Fill 10 buchtels with powidl and 10 with quark for a choice of flavors.
The Boss Kitchen editorial staff oversees content review, fact-checking, and recipe verification across the site. Published articles pass through the editorial team before going live, ensuring ingredient lists, techniques, cooking times, and nutritional claims hold up in a home kitchen. The team coordinates contributions across the site writers, handles reader corrections, and maintains consistency in measurement conventions, safety guidance, and dietary labeling. Posts under this byline typically represent team-reviewed reference material, site announcements, or editorial roundups rather than individual-author features, and they are held to the same sourcing standards as bylined recipe and product coverage.