Special equipment: two 6-inch cake pans; a candy thermometer; a kitchen blowtorch
For the cake: Preheat the oven to 350 degrees F. Spray two 6-inch cake pans with nonstick spray and line the bottoms with parchment circles.
Mix together the flour, graham cracker crumbs, baking powder, baking soda and salt in a medium bowl.
Combine the butter, oil, granulated sugar, brown sugar and corn syrup in a stand mixer fitted with the paddle attachment. Mix on medium speed for 3 minutes. Add eggs and vanilla and mix until combined. On low speed, add one-third of the flour mixture, followed by half of the milk, mixing until combined. Repeat. Add the final third of the flour mixture and mix for 30 seconds.
Divide the batter between the prepared cake pans. Bake until set in the center and an inserted toothpick comes out clean, 20 to 25 minutes. Allow the cakes to cool in the pan for 10 minutes, then invert onto a wire rack. Let cool completely.
For the buttercream: Combine the granulated sugar and water in small pot fitted with a candy thermometer. Boil to the soft ball stage.
Meanwhile, whip the egg whites and cream of tartar with an electric mixer on medium speed until soft peaks form.
When the sugar syrup reaches 225 degrees F, add it slowly to the whipped egg whites while beating on medium speed. Continue beating until cool. With the mixer running, add the butter a few pieces at a time. Mix in the vanilla extract and fold in the marshmallow creme.
Spread the marshmallows out on a foil-lined baking sheet. Toast with a kitchen blowtorch, moving the marshmallows around to make sure both sides are toasted. Add half of the toasted marshmallows to buttercream. Set aside the other half. (Makes 4 cups.)
For the ganache: Place the chopped chocolate in a heatproof bowl. Bring the cream just to a boil in a small saucepan over medium-high heat. Pour the hot cream over the chocolate and let stand for 10 minutes. Stir until shiny and smooth. Add the butter and stir until completely melted. Let cool at room temperature until set, about 1 hour. (Makes 1 1/2 cups.)
To assemble: Level the tops of the cakes, then slice each in half horizontally (to make four layers). Starting with the bottom layer, spread the top with about a 1/4-inch of ganache. Place the next cake layer on top, spread with a 1/4-inch of buttercream and sprinkle with the reserved toasted marshmallows. Add the third cake layer and another layer of ganache. Place the final cake layer on top. With an offset spatula, remove any excess filling from the outside of the cake. Refrigerate for 15 minutes to set. Once the cake has chilled, ice the entire cake with the remaining buttercream.
This recipe was created by a contestant during a cooking competition. It has not been tested for home use.
Propane gas torches are highly flammable and should be kept away from heat, open flame and prolonged exposure to sunlight. They should be used only in well-ventilated areas. Follow torch manufacturer's instructions for use.