Wash potatoes and beet thoroughly. Cook separately in boiling water for about 15 minutes. Peel and finely dice onion.
Knead minced meat, egg yolk, breadcrumbs and onion. Season with salt, pepper and mustard. Shape into 4 meatballs with moistened hands. Drain potatoes and beet, cut in half and score the cut surface more often. Insert bay leaves and sprinkle with thyme. Sprinkle with coarse salt and pepper.
Spread everything on a baking tray lined with baking paper. Bake in a preheated oven at 175 degrees for 20-25 minutes. Wash and pluck the chives and parsley and finely chop all but a little.
Mix curd cheese and herbs. Season with salt, pepper and lemon juice. Arrange everything with a blob of quark. Serve the rest of the curd with it. Garnish with remaining herbs.