A little butter or margarine Fry the onion, without browning, in the butter or margarine. When soft add the hot water; when the fragments of the onion are fully cooked, add the milk to increase the measure to about a quart, and as soon as it boils add in the flour mixed smooth with milk. Season to taste, stir and simmer until it thickens. A moment or so before serving, mix in the cheese.