Baking may not seem hard until you try doing it. The elements of science at play that you may not even be aware of could be the reason why your buttercream frosting is too thin. For example, when making a whipped cream topping for pies or cakes, everything from the ingredients to the beats and bowl must be cold. These kinds of toppings, like whipped cream or buttercream frosting, can be over-beaten, which will cause the frosting to be too thin. Frostings that call for wetter ingredients like Greek yogurt require more dry ingredients to thicken, though they will also set slightly more in the fridge. With a bit of reading, you will come to find sugar is not the only way to thicken a thin frosting.
Ingredients for Thickening Frosting
Powdered sugar is one of the most common ingredients for thickening frosting. Frosting is already sweet, so the sugar does not add much more sweetness, but it does add volume. And, since it's a dry ingredient, it absorbs the extra liquid. If you are trying to avoid adding more sugar to an already sweet dessert, try adding a flavor-appropriate thickening agent to your frosting. These thickening agents include: cornstarch, gelatin, cream cheese, cocoa powder, cold heavy cream, tapioca, arrowroot starch, flour and even butter.
How to Thicken Frosting by Adding Ingredients
The ingredient that should be added to a frosting depends on the kind of frosting it is. For example, flour should be added only to cooked frostings and cocoa powder should be added only to chocolate frostings. No matter the added ingredient or the type of frosting, however, always start with a small amount, usually one teaspoon, of the thickening agent and add more as needed.
Other added ingredients are also specific to particular types of frosting and are fairly self-explanatory. Cream cheese frosting usually thickens when it is refrigerated, but if it is still too thick, add a tablespoon or two at a time of softened cream cheese, taking care not to over-whip the frosting. Once you're sure the frosting has thickened enough, place it in the fridge to continue to harden. Buttercream frosting can also be thickened with butter in the same fashion.
A couple of tablespoons of cold heavy cream can be used to help thicken whipped cream frosting, cream cheese frosting, buttercream frosting or even marshmallow frosting for cake, but the cream, beats and bowl must be very cold and don't over whip the cream.
Cornstarch, tapioca and arrowroot starch are the most versatile thickening agents, meaning they can be used in almost any frosting. To use one of these starch add-ins, begin with two teaspoons. Pour the teaspoons of powder into a grinder, like a coffee bean grinder or a small food processor, and pulse until the powder is extra fine. Add half a teaspoon at a time to the frosting, stirring well between each addition, until the frosting is thick.
Gelatin is often used to stabilize or thicken whipped cream, buttercream and cream cheese frostings. Make unflavored gelatin and allow it to completely cool. Add two tablespoons of gelatin while whisking the frosting together, then let it chill in the fridge for about 10 minutes.
Will Icing Thicken in the Fridge?
Icing will thicken in the fridge too, so there are options for soft frostings that do not involve adding more ingredients. Warm frosting can quickly become runny, but even if the icing is not warm, try popping it in the fridge for a while. Be sure to tightly cover the top of the mixing bowl that holds the icing with plastic cling wrap before placing in the fridge. Frosting that is not covered in the fridge, especially cream cheese frosting, will develop a hardened skin. If the frosting is a cooked frosting, try cooking it on the stovetop a bit longer.