Preheat your oven to 350°F (175°C). In a mixing bowl, combine crushed chocolate graham crackers, melted butter, and granulated sugar until the mixture resembles wet sand. Press this crumbly mixture into the bottom and up the sides of a tart pan. Bake for 10 minutes or until slightly firm, then remove and let it cool completely.

In a small bowl, sprinkle unflavored gelatin over cold water. Allow it to sit for 5 minutes to bloom. Heat the mixture in the microwave for about 15 seconds or until dissolved, then set it aside to cool slightly.

Melt white chocolate chips in a heatproof bowl over simmering water, stirring until smooth. Combine the melted chocolate with milk or cream, then whisk in the cooled gelatin and pure peppermint oil. Allow this mixture to cool to below 85°F.

In a separate bowl, beat heavy whipping cream and powdered sugar until medium-stiff peaks form. Gently fold the whipped cream into the chocolate mixture.

Spoon the mousse into the cooled crust, smoothing the top. Cover with plastic wrap and refrigerate for several hours or overnight to set.

In a saucepan, heat cream until boiling. Stir in chocolate until melted and smooth. Blend in corn syrup and warm water until glossy. Let it cool slightly.

Once the mousse has set, pour the glaze over the tart and set at room temperature for 1 hour before serving.