Mascarpone is an optional ingredient, however, I recommend using it. It can stabilize the whipped cream, improves its texture, and makes it harder to overwhip.
Place very cold 36% fat content heavy cream into a mixing bowl along with the sifted powdered sugar and start whipping it on medium-high speed.
When the frosting reaches sour cream consistency, add the vanilla extract, cocoa powder, and mascarpone (if using) and continue whipping for about another minute or two.
When the frosting reaches a fluffy and pipeable consistency (early hard peaks, straight after soft peaks), stop whipping immediately. If you continue whipping, the frosting will separate, get runny, and then it will turn into butter.
Use this chocolate whipped cream frosting to fill, frost, or decorate your desserts according to your recipe.
The frosting can be refrigerated for 1-2 days and should not deflate if it was whipped up correctly.
Notes
The recipe above is enough to frost 6 cupcakes generously. To frost cakes, you will need approximately 3x for a 6-inch cake, 4x for a 7-inch cake, and 5x for an 8-inch cake (depending on how much frosting vs. sponge ratio you prefer on your cakes and whether you are using any other filling in between the layers)Ingredient notes:
Measure your ingredients with a Digital scale for accuracy.
The heavy cream needs to be high in fat (36%+). The low-fat version won't whip up correctly because it contains more water.
Sift the powdered sugar and cocoa powder before using.
Technique notes:
Make sure you read my Expert tips section above to maximize your success. A short recipe alone cannot cover all the necessary details and the science behind baking.
A whipped cream frosting is very easy to overwhip. When whipping, stop as soon as the mixture has reached a fluffy consistency (this will take 2-3 minutes) and early stiff peaks. It won't get stiffer after this point. In fact, if you overbeat it, it will only get runnier, and then it will break.