Toasted Marshmallow Chocolate Cake

Prepare two 9-inch cake pans by lining the bottom with parchment paper and lightly spraying them with baking spray. Preheat the oven to 175°C.

In a large bowl, combine the cake mix, eggs, milk, and melted butter. Use an electric mixer to beat the mixture until well combined. Mix in the espresso powder and 2 teaspoons of vanilla extract. Divide the batter evenly between the prepared pans, spreading it into even layers.

Bake in the preheated oven for 25 to 30 minutes or until a toothpick inserted into the center of the cakes comes out clean. Allow the cakes to cool in the pans on a wire rack for 20 minutes, then remove the cakes from the pans and let them cool completely on a wire rack.

While the cakes are baking, place the chocolate chips into a heatproof bowl. In a small saucepan, bring the cream to a gentle simmer over medium-low heat, stirring constantly for about 6 minutes. Pour the hot cream over the chocolate chips and let it stand for 5 minutes. Gently stir together until the chocolate mixture is thickened to a spreadable consistency, about 1 ½ hours.

In a separate saucepan, bring 2 inches of water to a simmer over medium-low heat. In a stand mixer fitted with a whisk attachment, beat the egg whites, sugar, and cream of tartar together on medium speed until well combined. Place the mixing bowl over the simmering saucepan, ensuring the bottom of the bowl does not touch the water. Cook the egg white mixture, whisking constantly, until a candy thermometer reaches 70°C and the sugar crystals have dissolved, about 8 to 10 minutes. Remove the bowl from heat and return it to the stand mixer. Beat on high speed, gradually adding the remaining 1 teaspoon of vanilla extract until stiff peaks form, about 6 to 7 minutes.

Set aside 2 cups of marshmallow cream. Place the remaining marshmallow cream into a piping bag fitted with a large star tip.

Remove the cooled cakes from the pans and discard the parchment. Using a serrated knife, trim the tops of the cooled cakes to create a level top. Place 1 cake layer on a cake stand or plate, cut-side up. Spread the reserved 2 cups of marshmallow cream in an even layer on the cake top. Sprinkle 1/2 cup of the graham cracker crumbs evenly over the top.

Top with the remaining cake layer, cut-side down. Fill in any empty spots in the seams of the cake layers using the marshmallow cream in the piping bag, and smooth the sides using an offset spatula. Refrigerate the stacked cake, uncovered, for 30 minutes.

Spoon 1 ¼ cups of the cooled chocolate mixture over the top of the stacked cake. Spread it into an even layer using a large cake spatula, allowing the excess to extend over the sides. Frost the sides of the cake using the remaining chocolate mixture, smoothing it into an even layer.

Using the marshmallow cream in the piping bag, pipe 10 large rosettes along the top, outside edge of the cake. Sprinkle the center of the cake with the remaining 1/4 cup of graham cracker crumbs.

Arrange the graham cracker rectangles upright on the long sides of each rectangle in a spoke-wheel design inside the rosette rings on top of the cake. Pipe 1 large rosette in the center of the graham cracker spoke-wheel design. Refrigerate, uncovered, until ready to serve, at least 30 minutes or up to 48 hours.

Just before serving, use a kitchen torch to slightly brown the marshmallow rosettes. Slice and serve the cake.