Put some onions to soak for ten minutes in boiling water. Peel them, cut in halves or quarters. Put them in a small saucepan with a lump of fresh butter; simmer very slowly until the onions are quite cooked, add salt to taste; thicken with flour, or flour and fine bread crumbs, and add cream or milk. Pass through a sieve, must be thick and smooth. Some people like a pinch of sugar.