2. To make the cheesecake layer, heat the cashew milk and gelatin in a large saucepan over low heat until the gelatin melts, about 2 minutes (or in the microwave for 10 seconds or until liquefied). Add the cream cheese, heavy cream, and sweetener and mix well with a hand mixer. Add the extract and food coloring, if using, and beat until smooth. Pour the batter into the bûche mold or lined loaf pan. Gently set the mold in the freezer while you make the chocolate mousse layer.
3. To make the mousse layer, heat the almond milk in the microwave or in a saucepan over low heat until hot, then set aside. Place 1 tablespoon of water in a small saucepan and whisk in the gelatin; let soften for 1 minute. Whisk in the egg yolks and sweetener, then stir in the hot almond milk. Cook over medium heat, stirring constantly, for 5 minutes or until the mixture thickens and coats a spoon. Add the 3 ounces of chopped chocolate and stir until the chocolate is totally melted, about 3 more minutes. Transfer the chocolate custard to a mixing bowl and place it in the refrigerator to cool slightly.
4. When the custard is just slightly warm, whip the cream until stiff peaks form. Gradually fold the whipped cream into the custard, then smooth the mousse over the cheesecake layer in the bûche pan and smooth the top. Cover and freeze for at least 3 hours or overnight, until firm.
5. To unmold, gently peel the sides of the silicone mold away from the bûche, pressing the top of the mold gently with your hand until the bûche releases. If you used a loaf pan, allow the bûche to thaw slightly, then use the overhanging paper to lift the bûche out of the pan. Place the bûche on a serving platter and set it in the freezer while you prepare the glaze.
6. To make the chocolate glaze, place the cream, sweetener, and chopped chocolate in a double boiler or in a heat-safe bowl set over a pan of simmering water. Heat on low, stirring, just until the chocolate is melted. Remove from the heat and stir in the vanilla. Pour the chocolate glaze over the cooled bûche. Cut into slices and garnish with mint leaves. Cover and refrigerate until ready to serve.
7. Store extras in an airtight container in the refrigerator for up to 4 days or in the freezer for up to 1 month.