S'mores Bundt Cake

INGREDIENTS

 * 1 ½ cup unsalted butter, softened at room temperature
 * 2 2/3 cups granulated sugar
 * 6 large eggs, at room temperature
 * 2 ¼ cups cake flour, sifted
 * ⅔ cup finely ground graham cracker crumbs
 * 1 ½ teaspoon kosher salt
 * ½ teaspoon baking soda
 * 1 cup whole buttermilk, at room temperature
 * 2 tablespoons pure vanilla extract
 * 1/4 cup black cocoa powder
 * ½ teaspoon espresso powder

MILK CHOCOLATE GANACHE:

 * 6 ounces milk chocolate bars, chopped
 * ⅓ cup heavy whipping cream

TOPPINGS:

 * Large marshmallows
 * Garnish: broken milk chocolate bars, roughly crushed graham crackers

INSTRUCTIONS
any air bubbles.
 * 1) Preheat oven to 325 degrees F. Grease a 12-cup bundt pan with baking spray. Freeze pan for about 20 minutes, as you prepare the batter.
 * 2) In the bowl of a stand mixer with the paddle attachment, cream the butter and sugar, on medium speed until light and fluffy, about 5-6 minutes.
 * 3) Add in the eggs, one at a time and mixing between each addition. Scrape down the bowl as needed.
 * 4) In a separate medium bowl, whisk together the flour, graham cracker crumbs, salt, and baking soda. In another small bowl, whisk the buttermilk and vanilla extract.
 * 5) Reduce the mixer to low. Alternatively add in the flour mixture and the buttermilk, beginning and ending with the flour, beating until just combined after each addition.
 * 6) In the medium bowl, transfer about 4 cups batter. Add in the cocoa powder and espresso powder. Fold in until well combined.
 * 7) Spoon 1 cup of the black batter into a large piping bag. Cut off the tip of the piping bag. Spoon 1 cup of the plain batter into another large piping bag. Cut off the tip of the piping bag. Into the prepared pan, alternatively pipe batters directly into the grooves to within ¾ inch o the top of the center tube and the outside rim. Use an offset spatula to carefully spread batter into the grooves and up the sides of the pan. Continue to alternatively pipe and spread more batter into each groove, closing any gaps between the batter.
 * 8) Refill the piping bags with remaining batter and repeat the process until there is no more. Tap the pan on the counter to spread the batter into grooves and remove
 * 1) Bake the cake until a cake tester inserted into the center comes out clean, about 45-50 minutes. Let cake cool in the pan for 10 minutes. Loosen the sides of the cake from the center of the pan. Invert cake onto a wire rack and let cool completely.
 * 2) To make the ganache, warm up the heavy cream in a microwave-safe bowl until hot. Pour the hot heavy cream over the chopped chocolate in a medium bowl. Let sit for 1-2 minutes before stirring until smooth. Use immediately.
 * 3) When ready to serve, transfer to a cake plate. Place the milk chocolate ganache into a large piping bag with a large round tip. Carefully pipe the ganache into the grooves of the cooled cake. Fill the center with large marshmallows. Using a kitchen torch, toast the marshmallows. Garnish the cake with graham crackers and chocolate.