Clean the leek, cut in half lengthways and cut into thin half rings. Blanch briefly in boiling salted water, then rinse in cold water and drain well.
Peel and finely dice the onion and garlic. Heat the rapeseed oil and fry the salmon fillet on both sides for 3-4 minutes on both sides (depending on the thickness of the fillet) in an open pan. The fish should still have a glassy core in the middle. Take the fish out of the pan. Now fry the onion and garlic cubes in the pan. Add the leek and stir-fry. Add the cream and let it boil down (the leek should still be firm to the bite). Salt and pepper the fried salmon, then cut into small cubes and fold into the leek vegetables together with the dill. Season to taste with salt, sugar, nutmeg and black pepper.