Peel the garlic. Cut 2 cloves into slices. Wash thyme, shake dry, remove leaves and chop coarsely. Wash lemon hot, grate dry and finely grate peel. Halve the lemon and squeeze juice from one half.
Mix with garlic slices, oil, thyme, 1 teaspoon sea salt and half of the lemon peel. Dab the meat dry, add to the marinade, cover and chill for at least 2 hours.
In the meantime, wash the potatoes and cook them in boiling water for about 20 minutes until al dente. Wash cucumber, grate dry and finely grate. Finely chop remaining garlic cloves. Mix with quark, cucumber and lemon peel.
Season to taste with sea salt, pepper and sugar. Cover and chill.
Drain the potatoes, rinse with cold water and peel. Let them cool down. Peel onion and cut into rings. Wash the chives, shake dry and, except for a few stalks for garnishing, cut into fine rolls.
Cut the potatoes into slices. Heat clarified butter in a large coated pan. Fry the potatoes for 5-8 minutes while turning them over. After half of the frying time add onions.
Season with salt and pepper. In the meantime, turn the steaks again in the marinade and fry them in a hot pan for about 3 minutes on each side.
Arrange steaks with fried potatoes and tzatsiki on plates. Sprinkle with chives and garnish. Serve with a mixed salad.