1. Add the raspberries, granulated sugar, and lemon juice to a saucepan over medium heat and cook until the berries break down and become saucy.

2. Press the raspberry mixture through a fine-mesh sieve into a bowl to remove the seeds.

3. Sprinkle the gelatin over the cold water in a small bowl and let it bloom for 5 minutes.

4. Stir the bloomed gelatin into the warm raspberry mixture until fully dissolved.

5. Let the raspberry mixture cool to room temperature.

6. In a separate bowl, beat the heavy whipping cream, powdered sugar, and vanilla extract until soft to medium peaks form.

7. Gently fold the cooled raspberry mixture into the whipped cream in batches until fully combined.

8. Spoon or pipe the mousse into heart-shaped silicone molds and smooth the tops.

9. Refrigerate for at least 4 hours, or until fully set.

10. Carefully unmold and garnish with fresh raspberries and a light dusting of powdered sugar before serving.