To begin, prepare the dough. In a large mixing bowl, whisk together the quark, eggs, granulated sugar, vanilla extract, and lemon zest (if using) until the mixture is smooth and well combined. This creates a creamy base for your Quarkbällchen, ensuring the flavours are evenly distributed.

In a separate bowl, sift together the flour, baking powder, and salt. Gradually add this dry mixture to the wet ingredients, stirring with a spatula or wooden spoon until a sticky dough forms. Avoid overmixing, as this can make the doughnuts dense.

Heat the vegetable oil in a deep pot or fryer to 170°C (340°F). To check the oil’s readiness, drop a small piece of dough into the oil. It should sizzle gently and float to the surface. Maintain this temperature throughout frying for consistent results.

Lightly oil your hands or use two teaspoons to form small balls of dough, roughly the size of a walnut. Work quickly to shape them evenly, as this ensures uniform cooking.

Carefully drop a few dough balls into the hot oil, making sure not to overcrowd the pot. Fry for 3-4 minutes, turning occasionally with a slotted spoon, until the Quarkbällchen are golden brown and puffed up.

Using the slotted spoon, transfer the fried doughnuts to a plate lined with paper towels to drain excess oil. Allow them to cool slightly while you fry the remaining batches.

Once all the Quarkbällchen are fried and slightly cooled, dust them generously with powdered sugar. For an extra indulgent touch, you can roll them in a mixture of cinnamon and sugar instead.

Serve the Quarkbällchen warm on a platter. Pair them with sides like fruit preserves or a dollop of whipped cream for added flavour. For an authentic German experience, enjoy them alongside a cup of freshly brewed coffee or tea. These delightful doughnut holes are perfect for sharing and bring a cosy, festive touch to any occasion.