Preheat Oven
Preheat your oven to 350°F (175°C). Line baking sheets with parchment paper and set aside.
Combine Dry Ingredients
In a medium bowl, whisk together the flour, baking soda, baking powder, and salt. Set aside.
Cream Butter and Sugars
In a large mixing bowl, beat the softened butter, granulated sugar, and brown sugar until light and fluffy (about 2-3 minutes) using an electric mixer or a whisk.
Add Egg and Vanilla
Add the egg and vanilla extract, mixing until well combined.
Mix in Dry Ingredients
Gradually add the dry ingredients to the wet mixture, mixing until just combined. Be careful not to over-mix.
Add the S’mores Mix-Ins
Gently fold in the chocolate chunks, mini marshmallows, and graham cracker pieces until evenly distributed throughout the dough.
Scoop and Bake
Scoop tablespoon-sized portions of dough onto the prepared baking sheets, spacing them about 2 inches apart. Slightly flatten each cookie, as they will puff up a bit while baking.
Bake
Bake for 8-10 minutes, or until the edges are golden brown and the marshmallows have begun to melt and caramelize. Be careful not to over-bake, as you want these cookies to stay soft and gooey.
Cool and Serve
Allow the cookies to cool on the baking sheet for a few minutes before transferring to a cooling rack. Enjoy warm for the best gooey marshmallow experience!