Dairy products are among the most versatile ingredients for cooks and bakers, in forms ranging from cold, fresh milk to hard grating cheeses. One of the more unusual options is sweetened condensed milk, made by combining evaporated milk with a high percentage of sugar. If you don't have any sweetened condensed milk on hand, you can cobble up a dairy- or non-dairy based substitute easily enough.
Getting the Ratio Right
Sweetened condensed milk is shelf-stable and won't curdle in acidic recipes, because -- like jams and jellies -- it contains enough sugar to stabilize and preserve the ordinarily perishable milk. That's about 20 percent sugar by weight if you're starting with whole milk, or a non-dairy milk equivalent, and 45 percent by weight once the milk is fully concentrated, explains Smucker's Foodservice. If you're starting from scratch with real dairy milk, or a drinkable substitute such as soy or rice milk, it's best to reduce the milk before you add the sugar. Otherwise, there's an unnecessarily high risk of scorching your milk as it reduces.
You'll need about a cup of concentrated milk per can of sweetened condensed milk in your recipe. If you're using whole liquid milk, start with 2 to 2 1/2 cups of milk -- the more you use, the richer the result -- and reduce it to 1 cup with gentle, slow simmering. Stir it regularly so it doesn't scorch, and then stir in 2/3 to 3/4 cup sugar once it's condensed. The larger amount is more authentic, but the smaller quantity works in most recipes. You can also begin with ordinary evaporated milk, using a blender or "stick" blender to dissolve the sugar.
Dry Milk Powder Method
Another simple substitution begins with dry milk powder, the ultimate form of concentrated milk. For every can of sweetened condensed milk your recipe calls for, you'll need 9 fluid ounces of dry milk powder -- a cup plus 2 tablespoons -- and 1/3 cup of hot water. Milk powder is made from nonfat milk, so you'll also need 2 to 3 tablespoons of melted butter as a replacement for the missing milk fat. Blend the ingredients until the sugar is thoroughly dissolved.
If you can't or won't eat dairy products, commercial alternatives to sweetened condensed milks aren't readily available. You can make your own by reducing your favorite non-dairy milk -- soy, rice, nut or coconut -- by gently simmering it, as you would with dairy milk. Simmer 2 1/2 to 3 cups of your chosen milk substitute down to 1 cup, and then add the same 2/3 to 3/4 cup of sugar you'd use with dairy milk. For a vegan version, use vegan-friendly raw or unfiltered sugars that aren't refined through bone charcoal. Non-dairy milks vary pretty widely, so if one doesn't do justice to your recipe, try again with a different type.
Off the Shelf
In recipes where its flavor is appropriate, at least one off-the-shelf product might be a suitable replacement for sweetened condensed milk. It's called creamed coconut -- not coconut cream, which is a very different product -- and is ordinarily used in cocktails. Thick, rich and heavily sweetened, like sweetened condensed milk, creamed coconut makes a fine substitute in fillings for cakes, pies and bar cookies. In candy-making it might or might not work, depending on your recipe, so be sure to make a test batch before you rely on it.