1. Preheat your oven to 350°F. In a bowl, combine the finely ground chocolate graham cracker crumbs, melted butter, and sugar. Press this mixture firmly into a 9-inch tart pan, ensuring the crust is evenly distributed. Bake for 8–10 minutes, then let the crust cool completely.

2. In a small bowl, sprinkle the unflavored gelatin over the cold water and let it sit for 5 minutes, allowing the gelatin to “bloom” and soften.

3. In a small saucepan, gently melt the white chocolate with the milk over low heat. Remove from heat and stir in the bloomed gelatin until it’s fully dissolved. Let the mixture cool slightly.

4. In a separate bowl, whip the heavy cream and powdered sugar until soft peaks form. Fold the whipped cream into the slightly cooled chocolate mixture, along with the peppermint oil, until the mousse is smooth and well-combined.

5. Pour the peppermint mousse into the prepared chocolate crust, smoothing the top with a spatula. Refrigerate the tart for at least 2 hours, or until the mousse is set.

6. In a small saucepan, heat the heavy cream until hot but not boiling. Remove from heat and pour the cream over the chopped dark chocolate. Let the mixture sit for 1–2 minutes, then stir until the chocolate is completely melted and the glaze is smooth. Add the corn syrup and warm water, whisking until the glaze becomes glossy and pourable.

7. Carefully pour the dark chocolate glaze over the set mousse, using a spatula to smooth the top. Refrigerate the tart for an additional 30 minutes to allow the glaze to set.