Evaporated milk is made by simmering milk to reduce the water — hence the name — and it's unsweetened. Condensed milk, on the other hand, is milk cooked with mega quantities of sugar. The result is a thick, pudding-like milk that's actually sweeter than cake frosting.
The primary thing to keep in mind is that evaporated milk is typically the liquid in a recipe, while sweetened condensed milk is used for its sugar, Castle says. That's largely due to how each style of milk is created.
"For evaporated milk, I think reduced milk would actually be the best description because they're cooking off some of the water," Castle says. "Milk has water, milk fat and milk solids in it. What you have left is milk that doesn't have any additives or anything in it, but it's a condensed version. It's a little bit thicker, it has a slight sweet taste — not because it's been sweetened — but because it concentrates the lactose in the milk. It just tastes a little bit richer."
Castle says recipes, including her grandmother's delicious fudge recipe, call for evaporated milk. Other recipes, such as broccoli cheddar soup, may call for evaporated milk. And Castle says she sometimes uses it in her coffee.
Condensed milk, also called sweetened condensed milk or "Eagle brand" after the milk's most common brand, follows a different, sweeter process. "It is milk cooked with a whole lot of sugar, and it's cooked until it reduces and thickens to the consistency of pudding," Castle says. "It's very thick and tends to be used as a free-standing ingredient. It usually fills the role of the sweetener." One 14 ounce- (414-milliliter) can of condensed milk is the equivalent of 1 quart (0.94 liter) of whole milk plus 7 ounces (198 grams) of sugar reduced.
Condensed milk is a staple ingredient in one of Castle's favorite Southern recipes: key lime pie. "You can't make good key lime pie without a can of Eagle brand [condensed milk]," she says. It's also used in common desserts like seven-layer bars.