In a small bowl, mix gelatin powder with water and let it bloom for 5 minutes.
In a mixing bowl, beat heavy whipping cream, sugar, and vanilla extract until soft peaks form.
Dissolve the espresso powder in a tablespoon of warm water and fold it into the whipped cream.
Gently fold in mascarpone cheese until smooth.
Melt the bloomed gelatin in the microwave for 10 seconds, then stir it into the mousse mixture.
Spoon the mousse into serving glasses and chill for at least 2 hours before serving.
Garnish with chocolate shavings and enjoy!