Preheat the oven to 350 degrees F. Add cupcake liners to a cupcake pan and set aside.
Add 15 graham crackers to a blender or food processor and mix until fine crumbs are formed.
In a small bowl add crumbs, 5 tbsp melted butter and 2 tbsp sugar. Mix until crumbs have been coated in the butter and a wet but sticky texture is achieved.
Put 1 Tbsp of the graham cracker mixture in each cupcake liner. Use a spoon to firmly press down the crumbs into a flat surface. (I used the top of a sprinkles lid and it worked great). Bake for 7 minutes and remove from the oven.
Meanwhile add all cupcake ingredients into a large bowl and mix on medium speed for 2 minutes. Add 2 Tbsp of batter into each cupcake liner. Bake for 17 minutes or until a toothpick inserted in the middle comes out clean.
Allow the cupcakes to rest in the pan for 5 minutes then transfer them to a cooling rack to come to room temp.
To make the frosting, cream 1 cup butter for 1-2 minutes on medium speed until it is light and fluffy. Add 1 jar of marshmallow cream and mix to combine. On a slower speed, add 1.5 cups of powdered sugar. Mix until combined.
Incorporate the remaining jar of marshmallow cream followed by another 1 ½ cups of powdered sugar. Continue to mix on high until a smooth, glossy frosting has formed.