How to Thicken Cake Frosting

Making cake frosting might not be as easy as you think. If you’re trying to fix a batch of frosting that turned out too runny, you're in the right place. This guide will share some helpful tips on how to thicken your frosting so it can be easily spread over your cake.

Add powdered sugar. Most frosting recipes already include powdered sugar, and the easiest way to thicken runny frosting is to gradually incorporate powdered sugar to balance out the liquid ingredients.

• Only add the sugar in small amounts. Sprinkle 1-2 tablespoons (15-30 ml) of powdered sugar into the frosting and mix well. Adding too much sugar at once can make the frosting overly sweet and too thick. If this happens, you'll need to add more liquid to balance it out, and the issue will return.
• Powdered sugar contains cornstarch, which helps absorb moisture and prevent the sugar from clumping.

Mix a bit of meringue powder with powdered sugar. To reduce the sweetness of the powdered sugar, you can also add a small amount of meringue powder. This will thicken the frosting without making it sweeter.

• Typically, if you add more than ½ cup (125 ml) of powdered sugar to thicken frosting, you should also add 1-2 teaspoons (5-10 ml) of meringue powder, especially if the frosting recipe already includes meringue powder.
• Meringue powder is made from egg whites, sugar, and gum. The sugar helps draw out moisture, while the gum acts as a natural thickening agent. However, using too much meringue powder can make the frosting too thick or dense.

Use arrowroot powder, cornstarch, or tapioca flour. These starches help absorb moisture and are excellent ingredients for thickening frosting without altering its flavor.

• Add about 1 tablespoon (15 ml) of starch to the frosting. Gently heat the mixture if the frosting can withstand higher temperatures and stir in the starch. Remove the mixture from the heat as soon as it starts to thicken.
• Cornstarch is probably the most commonly used for frosting, as it has little shine, virtually no flavor, and blends well with milk. However, cornstarch can freeze when exposed to low temperatures, so it’s not ideal for frosting that needs to be stored in the fridge. It's best used for frosting mixtures that are lightly heated on the stove and then cooled to room temperature.
• Tapioca flour has a high gloss and works well with more acidic liquids. It tends to become slimy when mixed with milk, but it’s a good choice if the frosting contains acidic dairy products like sour cream or buttermilk. Tapioca flour can thicken at relatively low temperatures, making it suitable for frosting that needs to be kept cool.
• Arrowroot powder also has a high gloss, but it can withstand cold temperatures and thickens at relatively low temperatures, making it a better choice for frosting that must be stored in the refrigerator.

Use flour only in cooked frostings. If you're heating the frosting on the stove, you can try thickening runny frosting with a little bit of flour.

• Do not use flour in recipes for cold frostings. Raw flour has a distinct flavor, and the only way to get rid of the raw flour taste is by cooking it. Thus, you can use flour in a frosting mixture that's being heated on the stove, but it’s not suitable for cold frostings that don't need cooking.
• Flour thickens most effectively when it’s heated.
• Sprinkle 1 teaspoon to 1 tablespoon (5-15 ml) of flour into the frosting mixture and stir over low heat until the mixture begins to thicken.
• Remove from the heat as soon as the frosting starts to thicken. If it’s cooked too long, the mixture may become runny again.

Try using soft cream cheese. If your frosting is too sweet and runny, you can add cream cheese to thicken it and enhance its flavor with a rich, contrasting taste that balances the sweetness.

• Add about 30 ml of cream cheese to the mixture and mix thoroughly. This ingredient works best in frostings that already include cream cheese in the recipe or in less sweet frostings.

Increase the amount of cocoa powder if appropriate. While not ideal for vanilla, cream cheese, or non-chocolate frostings, cocoa powder is worth trying if you're making chocolate frosting.

• Gradually add 1-2 teaspoons (5-10 ml) of cocoa powder at a time to avoid making the frosting too thick or too strong. Cocoa powder has a slightly bitter taste, so it may make the frosting more bitter.
• Cocoa powder is also a starch and can thicken liquids without needing to be cooked, making it a better choice than melted chocolate for thickening frosting.
• Unsweetened cocoa powder thickens better than chocolate with a bittersweet flavor. Cocoa contains more starch than chocolate.

Mix in some butter or shortening. If your frosting contains butter or shortening, you can use these ingredients to thicken the mixture if it's a bit runny.

• Add about 1 tablespoon (15 ml) at a time to avoid altering the flavor and consistency too much.
• Note that you might not see immediate results when using butter to thicken frosting. When the frosting warms up, the butter will melt, making the mixture runnier. To check the consistency accurately, chill the butter-based frosting in the fridge.

Consider adding a little heavy cream. For frostings that can be whipped and chilled, heavy cream is another ingredient to thicken the mixture without making it too sweet.

• Heavy cream will provide a rich, thick texture to your frosting mixture.
• This method works best if you plan to heat or whip the frosting after adding the heavy cream. When heated, the frosting will firm up and thicken more. Heavy cream will help make the frosting fluffier, thicker, and lighter.
• Add about ¼ cup (60 ml) of heavy cream. Too much heavy cream will make the mixture more runny.

Chill the frosting. Sometimes, frosting may appear too runny simply because it hasn’t had enough time to thicken. In this case, try chilling it in the fridge for 30-90 minutes.

• This method is most effective for frostings that have been cooked on the stove. Allowing it to chill helps it set better, as colder temperatures generally lead to thicker consistency.
• This approach also works for frostings made with buttercream or whipped cream. These ingredients are sensitive to heat, so the longer the frosting sits at room temperature, the more likely it is to become runny. Chilling can help restore the desired thickness.

Cook the frosting a little longer. If your frosting mixture that was cooked on the stove still seems too runny, you can thicken it by extending the cooking time.

• However, exercise caution when using this method. Overcooking could cause the frosting to burn or curdle. Be sure to stir continuously, and if the frosting doesn't thicken after a few minutes, remove it from the heat and try a different method.

Follow the recipe precisely. While making frosting may seem simple, even a small change in ingredients can drastically affect the thickness.

• For example, unsweetened chocolate will create a thicker frosting than bittersweet or milk chocolate. Cocoa powder contains starch, and unsweetened chocolate has a higher cocoa content, whereas sweeter chocolates have more sugar and less starch. So, if the recipe calls for unsweetened chocolate and you use a sweeter one, the frosting may end up runnier than expected.
• Similarly, cream cheese and milk can make a difference. While using whole milk or 2% milk won't impact the frosting much, using half-and-half (a mix of cream and whole milk) in place of regular milk could result in a thinner frosting. Low-fat cream cheese will also lead to a runnier frosting if the recipe requires full-fat cream cheese.

Combine ingredients in the correct order. Typically, the most liquid ingredients should be added last. You can follow this sequence to prevent the frosting from becoming too runny.

• If sugar and butter (or shortening) are mixed first, then add other liquids like water and milk afterward. This method ensures the frosting is easier to whip and spread, but you should be careful to avoid it becoming too runny.

Gradually add ingredients, one at a time and in small amounts. A common reason for encountering issues with the consistency of frosting is adding too much of one ingredient, which can spoil the entire batch.

• Both powdered sugar and liquids should be added gradually and in small quantities. If the frosting is too thick initially, you may need to add more liquid, but be careful not to overdo it, as this could cause the frosting to become too runny.

• Pot
• Mixing spoon
• Mixing bowl
• Hand mixer
• Fridge
• Stove