Preheat the oven to 350°F and prepare two 8-inch cake pans. Mix dry ingredients with eggs, milk, oil, vanilla, and hot coffee or water until smooth. Avoid overmixing to keep the cake soft and tender.
Divide batter between pans and bake for 30–35 minutes until a toothpick comes out with a few moist crumbs. Cool completely before frosting for easier assembly.
Make the graham cracker crunch by combining crushed graham crackers, melted butter, and brown sugar. Toast briefly if you want a deeper flavor.
Beat butter until creamy, then mix in powdered sugar, marshmallow fluff, vanilla, and salt until light and fluffy. Chill briefly if the frosting is too soft.
Assemble the cake with layers of chocolate cake, marshmallow frosting, and graham cracker crunch. Cover with frosting and decorate with toasted marshmallows, graham cracker pieces, and chocolate drizzle for the perfect s’mores finish.
