Heat the butter, and when foaming add the onions and cloves. Let the onions soften, but not color at all. Sprinkle over the flour, mix well and cook, stirring, for about 1 minute; then add the nutmeg, the bay leaf and the stock. Stir all the time until it boils, and see that it is smooth. Simmer until the onions are cooked, then gradually add the milk, stirring, and when that boils lift out the cloves and bay leaf.  . It can now be liquidized, or served as is with the cream added, and a sprinkling of grated cheese.