Cooking with Milk
To avoid the formation of a skin and to prevent milk from boiling over, always heat it gently at a low temperature. Scalding the milk, instead of boiling it, will also prevent a skin from forming.
Scald: To heat milk until the point of boiling, when some movement can be seen at the edges of the pan but there is no overall bubbling.
To prevent a skin appearing on a milk-based sauce (such as béchamel) as it sits, rub a small piece of butter over the surface; this will form a protective film over the sauce, which can be stirred in just before serving.
Alternatively, place a sheet of dampened greaseproof paper directly on the surface of the sauce.
