Start by gently washing and draining 2 cups of fresh blackberries. In a bowl, combine the blackberries with ¼ cup of granulated sugar and 1 tablespoon of lemon juice. Use a fork to mash the mixture slightly—keep some blackberry chunks visible for texture—until the sugar is dissolved.

In a small bowl, sprinkle 1 tablespoon of gelatin powder over 3 tablespoons of cold water and let it sit for about 5 minutes. After blooming, gently heat the mixture in the microwave for about 10-15 seconds or until fully dissolved, stirring continuously.

Once the gelatin is fully dissolved, pour it into the mashed blackberry mixture. Stir thoroughly to ensure the gelatin is evenly incorporated.

In a separate mixing bowl, pour in 1 cup of heavy whipping cream. Using an electric mixer, whip the cream on medium-high speed until soft peaks form, about 2-3 minutes. Fold in a small portion of the whipped cream into the berry mixture, then carefully fold in the remaining whipped cream.

Spoon the blackberry mousse mixture into serving dishes, cover, and refrigerate for at least 2 hours to allow the mousse to set properly.