In a small bowl, mix together the graham cracker crumbs, butter, and sugar. Set aside.
To make the cupcake base, mix all the wet and dry ingredients together until completely combined.
In a cupcake-lined muffin tin, press the graham cracker mixture into the bottom and slightly up the sides of the tin.
Fill the cupcake liners ½ of the way full with the cake batter and bake for 18-20 minutes or until a toothpick inserted comes out clean.
Let cool.
After the cupcakes are cooled, use a piping bag to pipe in a ½ tbsp of marshmallow fluff or use a small knife to cut a hole in the center of the cupcake before filling.
To make the frosting, cream the butter until fluffy, then add in the vanilla, milk, cocoa powder, and powdered sugar.
Using a piping bag or knife, ice the cupcakes and decorate with mini marshmallows and chocolate squares.
Baking pastry components without specialized tools requires adapting standard kitchen equipment into functional assets. A standard muffin tin lined with paper cups easily replaces commercial molds when constructing these chocolate cakes. Pressing the graham cracker crumb, butter, and sugar mixture directly into the base of each liner establishes a firm structural foundation for the batter. Mixing the crumb base thoroughly ensures the butter coats every particle, preventing a soggy crust once the batter releases moisture during baking. Oven temperature must remain steady at 350 degrees Fahrenheit to allow the crumb crust and the surrounding chocolate cake to set simultaneously without burning the exterior sugars. Testing doneness requires inserting a wooden toothpick into the center of the cake; it should emerge clean without wet batter clinging to the wood. Olive oil functions as the primary fat in the cake batter, yielding a dense, moist crumb compared to solid fats like shortening. Substituting oil for butter in the cake base changes the emulsion dynamics, requiring gentle mixing just until the wet and dry components combine to avoid gluten development. Cooling the baked bases completely before filling is mandatory; warm cake will liquefy the marshmallow fluff core upon contact. Piped fillings demand precision, requiring either a narrow pastry tip or a small paring knife to carve a central cavity without compromising the structural integrity of the cupcake walls. Creaming softened butter thoroughly before incorporating the powdered sugar and cocoa powder prevents grittiness in the chocolate frosting. Sifting the cocoa powder alongside the sugar eliminates lumps that frequently clog standard piping tips during the final decoration phase.