Preheat oven to 170°C. Mix Mediterranean seasoning with granulated garlic. Season the chicken thighs on all sides with salt and pepper, sprinkle with half of the resulting spice mixture, rub the spices into the meat and let lie under the film for 15 minutes.
Wash the potatoes with a brush and cut each potato into 4-6 easy-to-eat pieces. Peel the onion and cut into large feathers. Salt and pepper the potatoes and onions.
Line a large baking dish or baking sheet with parchment paper. Mix the thighs, potatoes and onions and drizzle with olive oil. Place in the center of the oven, bake for 25 minutes.
Mix the sour cream with the remaining spice mixture, add the nutmeg, a little salt and pepper. Remove the dish/tray from the oven, brush the chicken and vegetables with the sour cream using a pastry brush. Place in the top third of the oven and bake until nicely browned, about 10 more minutes. Serve hot.