Wash strawberries; pat dry.
Cut off the top of each strawberry and hollow out center; place cut side down on a dry paper towel and set aside.
Sprinkle gelatin over cold water in a small bowl; stir and let stand 1 minute to soften.
Add boiling water; stir until gelatin is completely dissolved. Mixture must be clear.
Stir together sugar and cocoa in small mixing bowl; add heavy cream and vanilla.
Beat at medium speed until stiff peaks form; pour in gelatin mixture and beat until well blended.
Refrigerate at least 30 minutes.
To fill strawberries, spoon mousse into a piping bag and pipe generously into hollowed out strawberries.
Sprinkle with cookie crumbs.