01 - 
                In a small pan, stir together the blackberries, sugar, and lemon juice. Cook over medium heat, stirring sometimes, until the berries soften and release their juices, which takes about 5 to 7 minutes.
              
              
              
                02 - 
                Run the cooked blackberry mix through a fine strainer to get rid of the seeds. Let the seed-free puree cool until it’s room temperature.
              
              
              
                03 - 
                Use an electric mixer or whisk to beat the cold cream with powdered sugar and vanilla. Keep going until stiff peaks hold their shape.
              
              
              
                04 - 
                Gently fold the cooled blackberry puree into the whipped cream until it’s totally mixed in. The mousse will be light and fluffy.
              
              
              
                05 - 
                Scoop or pipe the mousse into cups or bowls you’ll serve it in. Chill it in the fridge for at least 2 hours so it firms up. If you want, add some garnishes like fresh berries, whipped cream, and mint before serving.