Lightly coat a 9-inch springform pan with cooking spray. Mix the crushed Oreos, melted butter, and salt until evenly moistened. Press the mixture firmly into the bottom of the pan. Refrigerate while preparing the mousse.

Sprinkle the gelatin over 3 tablespoons of cold water. Let it stand for about 5 minutes until softened.

Place the chocolate chips in a heatproof bowl. Melt them in short microwave intervals, stirring after each interval, until smooth. Set aside to cool slightly.

Beat 2½ cups of the heavy cream until soft peaks form. Add the ½ cup powdered sugar and continue beating until medium peaks form. Keep the remaining ½ cup cream refrigerated for the decoration.

Gently warm the bloomed gelatin until completely liquid. Stir a small amount of the melted chocolate into the gelatin, then gradually mix it back into the remaining chocolate. This helps prevent gelatin lumps.

Gently fold the chocolate mixture into the whipped cream in several additions. Continue folding until the mixture is smooth and no white streaks remain.

Arrange the hulled strawberries over the chilled Oreo crust. Spoon the chocolate mousse over the strawberries and smooth the top using an offset spatula. Refrigerate for at least 6 hours, or until firmly set.

Beat the remaining ½ cup heavy cream, 2 tablespoons powdered sugar, and vanilla until medium peaks form. Pipe or spread the cream over the chilled cake. Add the strawberry slices or halves. Carefully remove the springform ring and slice using a sharp knife, wiping the blade between cuts.