Sprinkle gelatin in a small bowl. Add cold water and stir briefly. Let stand until the gelatin has soaked up the water,
about 1 minute or so.
Add boiling water to the bowl and stir until the gelatin is completely dissolved. Set aside to cool completely.
In a bowl of an electric stand mixer fitted with a whisk attachment (a hand mixer works wonderfully here too) combine 1 cup of sugar
pour then strawberry powder. Add the heavy cream and mix over medium/high speed until the mixture thickens. Slowly pour, the
strawberry puree, followed by the vanilla extract, and finally the gelatin mixture.
Increase the speed to high and continue whisking until thickened, about 2 minutes or so. Stop the mixer. Taste and add more sugar,
1 tablespoon at a time until the desired level of sweetness is reached. Remove bowl from mixer and test thickness by dipping the whisk into the mousse and lifting. If the mousse does not immediately dissolve onto itself it's ready. You want the mousse thick enough to form shapes that will not dissolve easily.
Spoon the mousse into a container with a tight-fitting lid and place in the freezer to chill for at least one hour.