In a large mixing bowl, pour in the cold heavy cream and whip the cream with an electric mixer on medium speed for a minute.
Sift cocoa powder and powdered sugar into the cream. Mix with a spatula until well combined.
Increase the mixer speed to medium-high and continue whipping until the mixture forms stiff peaks.
Spoon the cocoa mousse into a piping bag with a piping tip. Pipe into serving glasses. Refrigerate for at least 4 hours.
Remove the cocoa mousse from the fridge and let it rest for 20 minutes before serving.
Garnish with a dollop of whipped cream and chocolate shavings.
Notes
Pick Good Cocoa Powder: The taste of your mousse comes from the cocoa powder, so choose a high-quality, unsweetened one for a deep chocolate flavor.Keep Ingredients Cold: Make sure your heavy cream is really cold before whipping. You can even chill the mixing bowl and whisk in the fridge or freezer for 15 minutes. Cold cream whips up faster and stays firm longer.Sift for Smoothness: Always sift the cocoa powder and powdered sugar before adding them to the cream. This helps avoid lumps and gives you a smooth, even mix.Don’t Overwhip: Stop whipping as soon as stiff peaks form. If you whip too long, the cream can curdle and turn into butter.Chill the Mousse: Let the mousse set in the fridge for at least 4 hours. This makes the texture firmer and the flavors richer.Piping Tips: If you’re using a piping bag, choose a large round or star tip for a pretty look. Fill the bag halfway for better control.Garnish Right Before Serving: Add garnishes like whipped cream or chocolate shavings just before serving, so they stay fresh and look great.Serve: Let the mousse at room temperature for 20 minutes before serving for the best texture and flavor.Adjust Sweetness: If you like it sweeter, you can add a bit more powdered sugar, but be careful not to overpower the cocoa taste.Storage: Store leftover cocoa mousse in an airtight container in the refrigerator for up to 3 days to maintain its freshness and texture.