Wash the chives, dab dry and cut into small rolls. Season yoghurt with salt and cayenne pepper. Fold in the chives. Cover and chill. Peel, wash and coarsely grate the pumpkin.
Wash the parsley, dab dry and pluck the leaves from the stalks, except for some for garnishing. Roast pumpkin seeds in a pan without fat. Let it cool down and, except for a few to garnish, roughly chop the onion and garlic.
Press the garlic through a garlic press. Finely dice the onion. Grate cheese. Knead minced meat, breadcrumbs, egg yolk, pumpkin, parsley, chopped pumpkin seeds, cheese and onion. Season with salt and cayenne pepper.
Form 12 meatballs from the mixture. Heat the oil in a pan. Fry the meatballs all around for 8-10 minutes. Serve with yoghurt sauce and garnish with remaining pumpkin seeds and parsley.