preheat your oven to 350 degrees F. sift the dry ingredients into the bowl of an electric mixer. add all of the wet ingredients (except the coffee) and beat well until combined.

stir in the hot coffee. the batter will be very thin. set aside.

place the graham crackers in a ziploc bag and seal. use a rolling pin to crush the graham crackers into fine crumbs. pour the graham cracker crumbs into a bowl and mix with the melted butter. add more melted butter as needed, until all of the graham cracker crumbs are evenly wet.

Grease and flour the sides of two 9-inch round cake pans, and line the bottoms of the cake pans with parchment paper. pour the graham cracker crumbs into the bottom of one of the cake pans. press the crumbs firmly in the bottom of the pan with your hands.

pour part of the cake batter over the graham cracker layer, and pour the remaining batter in the second cake pan until it is about 2/3 of the way full. (you will have leftover cake batter. you can bake off the rest of the batter in another cake pan or in smaller ramekins.)

bake the cakes for 30-35 minutes, or until a knife inserted in the center of the cakes comes out clean. once baked, allow the cakes to cool in the cake pans for 10 minutes, then remove the cakes from the pans and allow them to cool completely on a wire cooling rack.

in the bowl of an electric mixer, cream the butter. add the vanilla extract and the marshmallow fluff. whip together, then gradually add the powdered sugar. add more powdered sugar as needed to reach your desired consistency.

in the bowl of an electric mixer, cream together the butter and cocoa powder. the mixture will be very thick. add the powdered sugar, vanilla, and milk. beat to incorporate. in a separate bowl, stir together the half-and-half and the ovaltine. pour the mixture into the frosting, and beat until incorporated. add more powdered sugar as needed to reach your desired consistency.

place the cake that has the the graham cracker layer on a cake stand so that the graham cracker layer is facing up. pipe a ring of chocolate frosting around the outer top edge of the graham cracker layer. (this will help to insure that the marshmallow filling does not ooze out the sides.) evenly spread the marshmallow filling inside of the chocolate frosting boarder.

place the cake in the refrigerator for 10-15 minutes to allow the marshmallow filling to harden up. place the second cake on top of the marshmallow filling. frost the entire cake with the chocolate buttercream frosting. place segments of graham crackers around the outside of the cake.

cut several large marshmallows in half with a pair of kitchen scissors. place the marshmallows, cut side down, on the top of the cake. use a kitchen torch to toast the marshmallows. cut several mini marshmallows in the same fashion and place them around the outside of the cake.