Graham cracker crust
1 1/2 cups finely ground graham cracker crumbs
1/3 cup sugar
6 tablespoons margarine, melted
Chocolate Ganache Layer
1 cup (8 oz) unsweetened coconut milk (not cream of coconut), well mixed
9 oz bittersweet chocolate, finely chopped
Vanilla Marshmallow Layer
1/4 cup + 1 tablespoons (2.5 oz) cold water
2 teaspoons pure vanilla extract
1 1/2 tablespoons powdered gelatin (only real gelatin will work. Click here for more information on kosher gelatin)
6 tablespoons (3 oz) cold water
10 tablespoons corn syrup
pinch of salt
3/4 cups granulated sugar
Preheat the oven to 375. Generously grease a 9-inch tart pan with a removable bottom, making sure to get all the way to the top of the pan. Mix all crust the ingredients in a medium bowl. Press mixture firmly into the bottom of the prepared pan. Bake for 7-10 minutes, or until lightly browned. Place in the refrigerator while preparing the ganache.
For Ganache Layer
Place chocolate in a large bowl. Heat coconut milk until just boiling, either on the stovetop or in the microwave. Pour hot coconut milk over the chocolate and let sit for 5 minutes. Whisk gently until completely smooth. If some chocolate remains unmelted microwave the mixture on 50% power in 15 second intervals, whisking after each one, until the chocolate is completely melted. Pour into the prepared crust and refrigerate until firm, at least one hour.
For Marshmallow Layer
Combine the first three ingredients in a medium bowl and whisk until well blended and smooth. Set aside.
Combine second quantity of water, corn syrup, salt and sugar in a 4-quart saucepan and place over medium heat. When the mixture comes to a boil brush down the sides of the pan above the upper surface of the syrup with a clean, moistened pastry brush or paper towel to dissolve any remaining sugar crystals. Do not stir the syrup once it comes to a boil.
Place a candy or instant read thermometer into the syrup and continue to cook, without stirring, until syrup reaches 248F. Remove pan from heat and carefully stir in gelatin mixture.
Pour the mixture into the bowl of an electric stand mixer fitted with the whisk attachment. Starting at medium speed gradually increase the mixer speed to high. While the mixture is beating remove the tart with the ganache from the refrigerator. Beat the mixture for 10-12 minutes. When done it should look white and fluffy and the bowl will no longer be hot to the touch.
Using a wet spatula scrape mixture into prepared pan on top of ganache. Spread into a smooth even layer using a wet spatula (or well moistened hands). Set tart aside, uncovered, at room temperature for at least 4 hours or over night.
If desired, toast top of the tart with a kitchen torch or broiler. Press up on bottom of pan to release tart from the pan. If using the broiler let the tart sit for a little while before removing from the pan and cutting to allow time for the ganache to re-harden.