Prepare the Strawberries: Rinse, hull, and puree the strawberries in a blender until smooth.
Bloom the Gelatin (Optional): Sprinkle gelatin over cold water and let it sit for 5 minutes to soften.
Cook the Strawberry Mixture: In a saucepan, combine strawberry puree, sugar, and lemon juice. Heat gently, stirring until sugar dissolves. If using gelatin, add it here and stir until dissolved.
Cool the Mixture: Let the mixture come to room temperature.
Whip the Cream: Using a chilled mixing bowl, beat the heavy cream until it forms soft peaks.
Combine and Fold: Carefully combine the cooled strawberry mixture with the whipped cream, folding until well blended.
Chill: Spoon the mousse into serving glasses or ramekins and chill for at least 2–4 hours until set.
