Preheat your oven to 350°F (175°C). In a mixing bowl, combine finely ground chocolate graham crackers, melted unsalted butter, and sugar until it resembles wet sand.

Press the crust mixture into a 9.5-inch tart pan evenly and bake for 10 minutes. Allow cooling on a wire rack.

Bloom the gelatin in cold water according to package directions, then dissolve it in the microwave until clear.

Melt white chocolate chips with milk over low heat, stir in bloomed gelatin and peppermint oil until well combined.

Whip the heavy whipping cream with powdered sugar until medium-stiff peaks form. Gently fold it into the cooled chocolate mixture.

Spoon the mousse mixture into the cooled crust and smooth the top. Cover with plastic wrap and refrigerate for at least 4 hours or overnight.

Heat the heavy cream until just boiling, stir in chopped bittersweet chocolate until smooth, then mix in light corn syrup and warm water.

Once the mousse has set, pour the chocolate glaze over the tart, spreading it smoothly. Allow it to sit at room temperature for about one hour before serving.