Milk Converter

Dairy substitution, worked from fat content rather than from a memorised chart.

Every dairy product in this family is the same two things in different proportions: milk fat, and everything else. Fix the fat and you have fixed most of what the substitution needs to do, because fat is what tenderises a crumb, carries flavour and drives browning.

Fat content, by weight:

Weight per cup: whole milk 244 g (8.6 oz), half-and-half 242 g, heavy cream 238 g (8.4 oz), evaporated milk 252 g.

The published charts run rich, and this is worth knowing before you trust one. Nearly every substitution chart on the internet says a cup of whole milk can be replaced by half a cup of half-and-half plus half a cup of water. Do the arithmetic and that mixture is 5.6% fat, not 3.25%. The heavy cream version, a third of a cup plus two thirds water, comes out at 12%, which is not milk at all, it is roughly half-and-half. The old charts were written to produce something milk-like in a hurry, not something that matches, and in a forgiving recipe the difference rarely shows. In a custard or a bread dough it does.

Matched on fat, one cup of whole milk is:

• Skim milk, a full cup, plus about 3/4 tablespoon of melted butter
• Evaporated milk, 1/2 cup plus 1/2 cup water. This one the old chart gets right
• Half-and-half, 1/3 cup (0.30 to be exact) plus 2/3 cup water
• Heavy cream, 1 1/2 tablespoons plus a scant cup of water

Dilute with skim milk rather than water whenever you have it. Water balances the fat and nothing else. Thin a tablespoon and a half of heavy cream out to a cup with water and you get the right fat sitting in what is basically water: no protein, no lactose, no milk solids, so it will not brown, thicken or taste of much. Use skim milk as the diluent and every component lands close to real whole milk. The volumes barely change, because skim carries almost no fat either.

Going the other way, butter is the only practical fix, and you have to take out milk to make room for it. A cup of heavy cream from whole milk is about 0.55 cup milk plus 7 tablespoons butter. That is a lot more butter than the charts suggest, and it still will not whip. Whipping needs an intact fat globule structure that melted butter simply does not have, so this substitution works in sauces, soups and batters and fails in anything that has to hold air.

One swap to watch: evaporated milk and sweetened condensed milk are not the same thing, and they are not interchangeable. Evaporated is milk with roughly half the water removed, which is exactly why the 1:1 dilution works. Condensed milk has a large amount of sugar added, so dropping it into a savoury recipe will wreck it. Plant milks (oat, soy, almond) can usually fill in cup for cup, but they lack dairy fat and protein, so richness and browning suffer a little.