For the creamy potato-leek soup, first finely chop the onion and garlic. Clean leek and cut everything (white and green) into thin slices. Sauté everything in butter. Peel the potatoes and cut into cubes. Add together with the spices and pour in the vegetable broth. Cover and simmer for about 25 minutes. Mash the potatoes with a masher, add the sour cream, stir well and season with pepper and salt.
Decorate the creamy potato-leek soup with leek rings and thinly sliced mushrooms.