01 -
Place the fresh raspberries and granulated sugar in a small saucepan over medium heat. Stir occasionally, allowing the raspberries to break down and release their juices, about 5-7 minutes. Use a fine mesh strainer to press the raspberry mixture through, removing the seeds and leaving a smooth puree. Add the lemon juice if desired for a hint of tartness. Set the puree aside to cool completely.
02 -
If you'd like a firmer mousse, measure exactly 1 teaspoon of unflavored gelatin powder. Dissolve it in 2 tablespoons of cold water in a small bowl and let it sit for 5 minutes to bloom. Once bloomed, microwave the gelatin for 5-10 seconds until it melts, then let it cool slightly. Stir the melted gelatin into the raspberry puree once it has cooled to room temperature.
03 -
In a large mixing bowl, add the chilled heavy whipping cream, powdered sugar, and vanilla extract. Using an electric mixer, whip the cream until it forms stiff peaks. Be careful not to over-whip, or it will turn grainy.
04 -
Gently fold the raspberry puree into the whipped cream, one-third at a time, until it's fully combined. The mixture should be light pink and airy. If using gelatin, the mixture will start to set as it chills, giving the mousse a more structured texture.
05 -
Spoon or pipe the mousse into serving glasses or dessert bowls. Refrigerate for at least 2 hours to allow it to firm up and for the flavors to meld.