Making the Dough:

1. Mix Butter and Sugar: Beat the butter with an electric mixer for 30 seconds at medium speed. Add the brown and white sugar, and beat for another 2 minutes until fluffy and light.
2. Add Egg and Vanilla: Beat in the egg, scrape the bowl, then add the yolk and mix. Add vanilla extract and mix on low.
3. Combine Dry Ingredients: Add flour, baking powder, baking soda, salt, and graham cracker crumbs. Mix on low until the dough forms.
4. Add Mix-Ins: Stir in the chocolate chips, chopped graham crackers, and 3/4 cup mini marshmallows. You can chop the marshmallows roughly to prevent them from expanding too much.
5. Shape Dough Balls: Scoop out a heaping tablespoon of dough for each cookie, forming about 26 balls. Roll each between your hands to make them smooth.
6. Top and Chill: Place a piece of Hershey’s chocolate on top of each cookie. Chill the cookies in the fridge for at least 1 hour, or freeze until solid (about 15-30 minutes).

Baking the Cookies:

1. Preheat Oven: Set your oven to 350°F.
2. Bake: Arrange the cookies on a baking sheet about 3 inches apart. Bake for 10 minutes.
3. Add Marshmallows: Open the oven and place 2-3 mini marshmallows on top of each cookie. Bake for another 2 minutes. You can use the broiler to toast the marshmallows for 1 minute, but watch closely to prevent burning.
4. Cool: Remove from the oven when edges are browned and tops are golden. Sprinkle extra graham cracker crumbs on top while hot. Cool for 10 minutes, then transfer to a wire rack.