Reach for non-flavored gelatin granules to thicken a frosting, rather than the highly sweetened, colored types. Just a spoonful or two of this gelatin can thicken frosting so it spreads more easily, keeps its shape and remains firm. If you bake frequently, make a large batch of the gelatin mixture and refrigerate it for up to three weeks. Melt it in the microwave before you use it.
To use gelatin to thicken frosting, soften -- or bloom -- a bit of nonflavored gelatin in cold water for five minutes. Gently heat it in the microwave, just until the individual granules dissolve. Stir in a bit of warm whipping cream to temper the gelatin and keep it from clumping when you add it to cold ingredients. To add gelatin to whipping cream, whip the cream until soft peaks form. Add sugar, vanilla and the gelatin, and continue whipping until stiff peaks form. To add the gelatin mixture to buttercream or cream cheese frosting, simply make the frosting and whip in the gelatin at the end.
Gelatin is most frequently added to a whipped cream frosting. Heavy cream more than doubles in volume when it's whipped, but sadly, this volume quickly deflates within 24 hours, becoming a disappointing, watery mess. Gelatin helps stabilize the whipped cream so it keeps its volume for two to three days. Stabilized whipped cream is stiff enough that you can pipe it. You can also add gelatin to a simple American buttercream, made with confectioner's sugar, butter and milk, or a cream cheese frosting. Cream cheese frosting is basically an American buttercream enriched with cream cheese. Both these frostings are relatively thick to begin with. Adding gelatin offers some added insurance that the frosting will remain stiff -- an especially good idea if you're serving the cake on a warm day.
For a simple dollop of whipping cream, don't go to the trouble of adding gelatin. The gelatin will make the whipping cream stiff. However, stabilized whipping cream works beautifully for frosting cakes. Use an offset spatula to smooth it over the sides and top of a cake, or fill a pastry bag with the prepared cream and pipe decorative scallops. Use the same approach when decorating with buttercream or cream cheese frosting.
Keep It Fresh
Adding gelatin to frosting helps keep it firm and stable, but perishable frostings must still be refrigerated. Chill a cake frosted with whipped cream or cream cheese frosting in the refrigerator for 15 to 20 minutes to harden the frosting slightly. Then wrap the cake loosely in plastic wrap and return it to the refrigerator. Use the cake within three to four days. For best flavor, bring the cake to room temperature before serving it.