When frosting for a cake, cupcakes, cookies or any other sweet treat becomes too thin, thickening it is a necessary step. Otherwise, the frosting will not create the desired appearance, especially for cakes and cupcakes. Sometimes you would rather not add more sugar, especially when the frosting is already very sweet. Fortunately, it is possible to thicken the frosting without the addition of sugar.
Thicken with cornstarch. Pour 2 tsp. of cornstarch into an electric grinder and grind until it forms a soft powder. Add a small amount, about 1/2 tsp., at a time and mix it into the frosting with a whisk or a mixer. Cornstarch will thicken the frosting, but must be ground to prevent clumping.
Thicken with heavy cream. Add 3 to 4 tbsp. heavy whipping cream to the frosting and whip it with a mixer until it thickens and becomes frothy. Add additional small amounts of cream at a time, if necessary, starting with 1 tbsp. at a time until it reaches the desired consistency. Otherwise, use a whisk and beat by hand until it gets thicker. The heavy whipping cream will not only make it thicker, but it will also make the frosting lighter and fluffier.
Thicken with coconut. If the frosting is a coconut flavor or will not clash with the added flavor of coconut, shredded coconut can help thicken it. Add 1 tbsp. of coconut at a time and mix well. Gradually add 1 tbsp. at a time until the frosting reaches your preferred thickness.
Thicken with gelatin. Gelatin is a thickening agent used in making marshmallows and fruit-flavored gelatins. Mix 1/2 tbsp. plain gelatin with 1/2 tbsp. of cold water until it dissolves and then stir the mixture into the frosting. Mix well and then put the frosting into the fridge to thicken.