In a small bowl, combine 1 tablespoon of gelatin with ½ cup of water and let it rest for 5 minutes until it develops a sponge-like consistency.
Set the bowl with the gelatin in a heatproof container filled with hot water. Stir until fully dissolved, then let it cool slightly before incorporating it into the mousse mixture.
Strawberry mixture
In a small saucepan, mix 1 pound of strawberries with 3 tablespoons of granulated sugar.
Heat over medium heat for about 10-15 minutes, until the strawberries soften, the sugar dissolves, and the mixture thickens slightly.
Take it off the heat and allow it to cool completely.
Mascarpone cream
In a large bowl, whisk together 1 ¾ cups of mascarpone, 1/3 cup of heavy cream, ½ cup of powdered sugar, and 1 teaspoon of vanilla extract.
Whisk the mixture until it becomes smooth and fully combined.
Combine
After the strawberry mixture has cooled, blend half of it until smooth. Set aside the remaining half with whole strawberry pieces.
Carefully fold the blended strawberry mixture into the mascarpone cream.
Refrigerate the combined mixture for about 20 minutes to allow it to firm up slightly.
Just before assembling the mousse, stir the dissolved gelatin into the blended strawberry mixture.
In serving glasses, layer the mascarpone cream with whole strawberries, filling the glasses nearly to the top.
Top the mascarpone cream with 3-4 tablespoons of the strawberry-gelatin mixture.
If desired, garnish with fresh strawberries and white chocolate drops.
Refrigerate the assembled mousse for 2-3 hours to allow it to set.