Preheat your oven to 350°F and line a baking sheet with parchment paper.
In a large bowl, cream together the butter, granulated sugar, and brown sugar until light and fluffy. Add the pumpkin puree, egg yolk, and vanilla extract, and mix until well combined.
1/2 cup unsalted butter (softened), 1/2 cup granulated sugar, 1/2 cup brown sugar (packed), 1/4 cup pumpkin puree, 1 large egg yolk, 1 teaspoon vanilla extract
In a separate bowl, whisk together the flour, cinnamon, baking soda, and salt.
1 1/2 cups all-purpose flour, 1 teaspoon ground cinnamon, 1/2 teaspoon baking soda, 1/2 teaspoon salt
Gradually add the dry ingredients to the wet ingredients, stirring until just combined. Fold in the milk chocolate chips, crushed graham crackers, and mini marshmallows.
3/4 cup milk chocolate chips, 1/2 cup crushed graham crackers, plus more for topping, 1 cup mini marshmallows, plus more for topping
Using a cookie scoop or tablespoon, drop 1.5-inch balls of dough onto the prepared baking sheet, spacing them about 2 inches apart.
Gently press a few pieces of Hershey bar, a couple of mini marshmallows, and a few extra pieces of crushed graham crackers onto the top of each cookie before baking.
2 Hershey bars, broken into squares
Bake for 10-12 minutes, or until the edges are golden brown but the centers remain soft.
Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.