Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper or a silicone mat to prevent sticking.
In a large mixing bowl, beat together the softened butter, granulated sugar, and brown sugar until the mixture is light and fluffy (about 2-3 minutes).
Beat in the eggs one at a time, followed by the vanilla extract. Continue mixing until well combined.
In a separate bowl, whisk together the flour, baking soda, salt, and graham cracker crumbs. Gradually add the dry ingredients to the butter mixture and mix until just combined.
Gently fold in the mini chocolate chips, chopped chocolate (if using), and mini marshmallows. Be careful not to overmix to avoid deflating the marshmallows.
Using a cookie scoop or tablespoon, drop rounded scoops of dough onto the prepared baking sheet, spacing them about 2 inches apart. Press a few extra mini marshmallows and chocolate chips on top for an extra indulgent look.
Bake for 10-12 minutes, or until the edges are golden and the marshmallows begin to puff up. The centers should still be soft but will firm up as they cool.
Allow the cookies to cool on the baking sheet for about 5 minutes before transferring them to a wire rack to cool completely. Enjoy your gooey, chocolatey treats!