In a blender or food processor, combine the sliced strawberries, granulated sugar, and lemon juice. Blend until smooth.

Strain the mixture through a fine mesh sieve to remove seeds, if desired. Set aside.

In a large mixing bowl, whip the heavy cream and vanilla extract with an electric mixer on medium speed until soft peaks form.

Gradually add the powdered sugar and continue to whip until stiff peaks form.

Gently fold the strawberry puree into the whipped cream using a spatula, being careful not to deflate the mixture.

Continue folding until fully combined and the mousse is a light pink color.

Spoon the mousse into serving dishes or glasses and refrigerate for at least 2 hours to set.

Serve chilled, garnished with fresh strawberries or a dollop of whipped cream if desired.