Combine the hulled and sliced strawberries with sugar and fresh lemon juice in a blender or food processor. Blend until completely smooth, about 1-2 minutes. The lemon juice brightens the strawberry flavor and prevents the mousse from tasting overly sweet. Strain the puree through a fine-mesh sieve if you prefer a completely smooth texture without seeds, pressing gently on the solids to extract all the juice.

Pour the heavy cream and vanilla extract into a chilled bowl. Using an electric mixer or whisk, beat the cream on medium-high speed until stiff peaks form, about 2-3 minutes. I like to chill my mixing bowl in the freezer for 10 minutes before whipping—it helps the cream reach stiff peaks faster and creates a more stable mousse that won't weep over time. Stop beating as soon as you reach stiff peaks to avoid overwhipping.

Gently fold the strawberry puree from Step 1 into the whipped cream from Step 2 using a rubber spatula, folding just until combined with some light pink streaks remaining for visual appeal—avoid overmixing, which will deflate the whipped cream and make the mousse dense. Divide the mousse evenly among serving glasses and refrigerate for at least 2 hours before serving. The chilling time allows the flavors to meld and the texture to set slightly while maintaining its light, airy consistency.