Clean the onions and zucchini and cut into cubes. Clean and chop the garlic. Sauté the onion and garlic in a little oil and pour the vegetable stock over them. Stir in the zucchini and oatmeal and simmer for about 20 minutes. Finely puree the soup with a hand blender and then stir in the sour cream. Season well with nutmeg and possibly with salt and pepper.