Heat up the butter in a frying pan. Add finely chopped onion and sauté until the onion is translucent and soft. Add garlic and continue cooking 2-3 minutes. Add the nettle leaves, wait until they soften, season with salt and pepper. Transfer to a colander to drain all the liquid. Cool down. Finely chop the nettle leaves.
In a large bowl, combine cottage cheese, grated cheese, egg yolks, lemon zest and nutmeg. Mix thoroughly and add the chopped nettle.
Mix the flour carefully. Flour should be added so that the mixture becomes dry and thick, but not hard.
Dust the tray or baking sheet with flour. With a tablespoon dipped in hot water, form round dumplings. Arrange them on the tray so that they do not touch. Dust lightly with flour and refrigerate for at least 2 hours.
Boil water in a saucepan, salt. Drop the dumplings in small batches into slowly boiling water. After they float to the surface of the water, cook for another 6-7 minutes. The dumplings should be firm, not runny inside. Remove from water and lay on a towel to dry.
Serve with green sauce. To prepare it, mix nettle, parsley and basil leaves, pine nuts and garlic in a blender bowl. Add olive oil, salt and pepper to the resulting puree, stir.
Sprinkle the dumplings with grated cheese when serving.