Preheat the oven to 350°F. Line a baking sheet with parchment paper or spray with nonstick spray. Set aside.
In a large bowl, using a hand mixer, cream the butter and sugars together.
10 tablespoons salted butter, ½ cup brown sugar, ¼ cup granulated sugar
Beat in the egg and vanilla extract until incorporated.
1 large egg, ½ teaspoon pure vanilla extract
In a separate bowl, whisk the flour and baking soda together.
1½ cups all-purpose flour, ½ teaspoon baking soda
Add the flour mixture to the wet ingredients, little by little, beating lightly after each addition.
Reserve ½ cup each of the chopped chocolate bar, graham crackers, and marshmallows and set aside. Add the rest to the batter, and lightly beat until incorporated.
3.1 ounces milk chocolate bars, 3 graham cracker sheets, 1 cup mini marshmallows
Use a cookie scoop, to drop balls of dough, about 2 tablespoons in size, on a large cookie sheet.
Bake for 4 minutes.
Remove the cookies from the oven, and top the cookies with the remaining chocolate, graham crackers, and marshmallows.
Return the cookies to the oven and bake for another 1-2 minutes.