Wash, peel and cut the potatoes into cubes. Wash the leek and cut into rings. Lightly fry both in melted butter. Add the vegetable stock and cook for 15 minutes. Possibly puree very lightly with the hand blender (only a few pulses). Cut the salmon into bite-sized cubes and add to the soup. Let everything steep again for 5 minutes. Refine the soup with cream and sprinkle with dill. Serve hot.