Preheat the oven to 350°F Line 24 muffin tins with paper liners.

In a medium bowl, combine the graham cracker crumbs, baking powder and salt; stir together and set aside.

In the bowl of an electric mixer fitted with the whisk attachment, beat the egg whites on medium-high speed until soft peaks form. Transfer to a separate bowl and set aside.

Replace the mixer bowl and fit with the paddle attachment. Cream together the butter and sugar and beat on medium speed until light and fluffy, about 2 minutes. Mix in the egg yolks until well combined. Stir in the vanilla extract.

Add in the dry ingredients alternately with the milk on low speed, beginning and ending with the dry ingredients and mixing just until incorporated.

Using a rubber spatula, fold in about a third of the egg whites to lighten the batter. Gently fold in the remaining egg whites until completely incorporated.

Divide the batter evenly in tins, about 2/3 full. Bake the cupcakes for about 15 minutes or until a toothpick inserted in the center comes out clean. Allow the cakes to cool in the pans for about 5-10 minutes, then remove and let cool completely.

Combine ganache ingredients (semi-sweet chocoalte, heavy cream, and confectioners sugar) in a microwave-safe bowl. Microwave on high for 20-30 seconds. Whisk together until smooth. Chill in refrigerator until ready to use.

Once cupcakes are cool, cut divots into the middle of each cupcake (be sure not to cut all the way down to the bottom though). Fill with chocolate ganache.

Beat butter for marshmallow buttercream until fluffy. Beat in marshmallow creme until incorporated.

Add confectioner's sugar and beat until fluffy (3-5 minutes). If needed, add milk to achieve desired consistency.

Frost cupcakes with buttercream and garnish with graham cracker crumbs and chocolate.