In a bowl, mix the chocolate cookie crumbs and melted butter. Press the mixture into the bottom of a 9-inch springform pan to form the crust. Chill in the refrigerator while preparing the mousse.
In a saucepan, heat the heavy cream over medium heat until it just begins to boil. Remove from heat and add the chopped chocolate. Let it sit for a minute, then stir until the chocolate is completely melted and the mixture is smooth. Stir in the vanilla extract.
Pour the chocolate mixture over the chilled crust in the springform pan. Spread it evenly and refrigerate for at least 2 hours, or until set.
In a small saucepan, combine the sliced strawberries, sugar, and water. Cook over medium heat until the strawberries are soft and the sugar is dissolved.
In a small bowl, sprinkle the gelatin over 1 tablespoon of water and let it sit for a few minutes to bloom. Then, add the bloomed gelatin to the warm strawberry mixture and stir until completely dissolved. Let the mixture cool to room temperature.
Once the chocolate mousse layer is set, arrange the sliced strawberries on top. Then, pour the strawberry gelatin mixture over the strawberries. Refrigerate for another 2 hours, or until the gelatin is set.
Before serving, carefully remove the sides of the springform pan. Garnish with fresh strawberries and serve chilled.