Make the Cupcakes:

• Preheat oven to 350°F (175°C). Line a cupcake pan with 6 liners.
• In a bowl, cream together butter and sugar until light and fluffy.
• Add egg and vanilla extract, mixing well.
• In another bowl, whisk cinnamon, salt, baking powder, flour, and graham cracker crumbs.
• Gradually add dry ingredients to butter mixture, alternating with milk. Mix until combined.
• Divide batter evenly among cupcake liners.
• Bake for 18-20 minutes or until a toothpick inserted in the center comes out clean.
• Let cupcakes cool for 5 minutes in the pan, then transfer to a wire rack to cool completely.

Make the Marshmallow Filling:

• In a heatproof bowl over simmering water, whisk egg white, sugar, and cream of tartar until sugar dissolves and mixture is warm.
• Remove from heat and beat with a mixer until stiff peaks form.
• Stir in vanilla extract.
• Once cupcakes are cool, cut out a small hole in the center of each and fill with marshmallow mixture.

Make the Chocolate Buttercream:

• Beat butter until smooth.
• Sift powdered sugar and cocoa powder together, then gradually add to butter.
• Add vanilla extract and milk, one tablespoon at a time, mixing until fluffy.

Assemble the Cupcakes:

• Pipe or spread frosting over filled cupcakes.
• Garnish with graham cracker crumbs, mini chocolate chips, or marshmallows.