Half and half can be used in place of milk as long as the liquid is diluted slightly to take into account the higher fat content of half and half. It is recommended that half and half be used only as a substitute for whole milk.
When substituting half and half, add 1/4 cup water to 3/4 cup half and half to approximate the consistency of whole milk. If there is a little milk on hand but not enough for the recipe, combine 5/8 cup of skim milk with 3/8 cup half and half to achieve the same results. The amount of combined liquid added should be equal to the amount of milk called for by the recipe.