Caramel frosting adds a tasty, sweet topping to cake flavors such as chocolate and yellow cake. With just a few ingredients, you can develop deep caramel flavor and the attractive light-brown color. A key ingredient is condensed milk. How much sugar you add depends on whether you're using sweetened condensed milk or the unsweetened variety, usually sold as evaporated milk. The only difference between the two is whether sugar is added before the evaporated milk is pasteurized and canned.
What You Need
Caramel frosting requires some simple ingredients besides the sweetened condensed -- or evaporated -- milk. Add to that some brown sugar or powdered sugar, vanilla extract and about a half cup of butter. For a thicker mixture, include a couple of tablespoons of golden corn syrup as well. With sweetened condensed milk, 1/2 cup of brown or powdered sugar is sufficient, but double that if you're using evaporated milk.
Mixing It Up
Melting the butter over medium-low heat gives you the base for your caramelization, which browns all the sugar present and gives it that caramel flavor. Pour in the condensed milk, sugar and vanilla extract, and keep whisking it; letting it sit still makes it cook unevenly, and it can leave clumps in the sugar. The mixture needs to boil softly for about six to 10 minutes. You'll see it darken to a light brown and begin to thicken. Pour it into a bowl, and it will thicken slightly as it cools so you can spread it over your cake; spread it while it's still slightly warm so it can finish cooling over the cake.
Using a Thermometer
Instead of guessing when your frosting is the right consistency, using a candy thermometer can help. A candy thermometer is flat and wide with a clip on the back to hold it firmly to the side of your pot. Clip it to your pot with the base of the thermometer in the frosting as it gently boils. Your caramel frosting should cook until it reaches 225 degrees Fahrenheit.
For a thicker frosting, replace about half of the condensed milk with leftover cake batter, then cook normally. For a lighter, fluffier texture, add a couple scoops of whipped cream and beat the mixture in a mixer to your desired consistency. After you pull the frosting off the heat, you also can add items such as chopped pecans or sweetened flaked coconut.