Homemade Sweetened Condensed Milk

This recipe makes approximately one cup. The exact yield may vary slightly depending on the width of your pan and how long you simmer the mixture. It will look thinner while warm and thicken as it cools, so remove it from the heat while it still pours from a spoon.

Ingredients
2 cups whole milk
⅔ cup granulated sugar
1 tablespoon unsalted butter, optional
½ teaspoon vanilla extract, optional

Whole milk gives the finished condensed milk its creamy texture. The sugar adds sweetness and helps create the glossy consistency shown in the photo. Butter makes it a little richer, while vanilla adds a gentle flavor. Both are optional if you want a simpler mixture for recipes that call for plain sweetened condensed milk.

Instructions
Choose a suitable saucepan. Use a wide, heavy-bottomed saucepan with enough space above the milk for it to bubble gently. A wide pan exposes more surface area, helping the liquid evaporate. The heavy base helps prevent scorching.
Combine the milk and sugar. Pour the whole milk into the saucepan and add the granulated sugar. Set the pan over medium heat and stir until the sugar dissolves. You should no longer feel grains of sugar against the bottom of the pan when you stir.
Bring it to a gentle simmer. Watch the milk as it warms. When small bubbles appear near the edges and the surface begins to move slightly, reduce the heat to low. Keep the mixture at a gentle simmer throughout cooking. A rapid boil can cause it to rise in the pan, stick to the bottom, or darken too much.
Reduce the mixture. Simmer uncovered for about 50–70 minutes. Stir occasionally at first, moving the spoon across the bottom and around the sides of the pan. As the milk becomes thicker, stir more frequently. This is especially helpful during the final 15–20 minutes, when it can catch on the bottom more easily.
Check the consistency. The mixture is ready when it has reduced to approximately 1 cup and lightly coats the back of a spoon. It should flow slowly in a ribbon, similar to the condensed milk in the image, but it does not need to be as thick while hot. Pour a little onto a cool plate if you want to see how it behaves after cooling for a minute.
Add optional flavorings. Remove the saucepan from the heat. Stir in the butter until melted, followed by the vanilla, if using. Whisk gently until the mixture looks smooth and even.
Cool and store. Let the condensed milk cool, stirring it a few times as it does. Transfer it to a clean jar, cover, and refrigerate. It will thicken further once chilled. Stir before using.
Tips

Keep the heat low. Slow simmering is the key to a pale, creamy result. If the milk starts bubbling vigorously, lower the heat immediately. If your stove runs hot even on its lowest setting, move the pan partly off the burner for a moment, then return it once the bubbling settles.

Stir more often near the end. At the beginning, the mixture is thin and needs only occasional attention. Once it begins coating the spoon, check it regularly. Scrape the bottom gently with a silicone spatula or wooden spoon so a thick layer does not form there.

Look for reduction as well as thickness. Homemade condensed milk may seem too thin while it is hot. If it has reduced to about one cup and coats a spoon, let it cool before deciding whether it needs more cooking. Continuing to simmer it until it is very thick in the pan can make it too stiff after refrigeration.

Adjust a thick batch gently. If your condensed milk becomes too thick after chilling, stir in a teaspoon of warm milk at a time until it reaches the consistency you need. Warm the jar’s contents gently first if they are too firm to stir easily.

For a smooth finish, whisk while cooling. A thin skin may form on the surface as the milk cools. Stirring a few times helps blend it back in. If small lumps remain, you can pour the cooled mixture through a fine strainer before storing it.

Use plain condensed milk for baking. If a dessert recipe calls for sweetened condensed milk, you may prefer to leave out the vanilla and butter so they do not change its flavor. In coffee or as a dessert drizzle, both additions can be delicious.

Storage

Store homemade sweetened condensed milk in a clean, covered jar in the refrigerator for up to 5 days. Use a clean spoon each time you take some out. It may become noticeably thicker in the refrigerator; a good stir usually makes it smooth again.

Unlike an unopened commercial can, this homemade version is not shelf-stable. Keep it refrigerated rather than leaving it on the counter. If it develops an off smell, unusual color, or visible mold, discard it.