In a large bowl, beat together the softened butter, brown sugar, and white sugar until the mixture is light and fluffy. This should take about 2-3 minutes. Add the eggs and vanilla extract, and continue beating until everything is well combined.
To the wet mixture, add flour, baking soda, baking powder, and salt. Stir until the dough is smooth. Now, fold in the mini chocolate chips and mini marshmallows. Break up the graham crackers into small pieces and toss them into the dough as well.
Pop the dough into the fridge to chill for about an hour. This helps the cookies maintain their shape and prevents them from spreading too much while baking.
Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper or a silicone mat.
Scoop out the dough using a cookie scoop or a tablespoon, forming balls about 2 inches in diameter. Place them about 3 inches apart on your prepared baking sheet. For an extra touch, press a few more marshmallows, chocolate chips, and graham cracker pieces into the top of each cookie.
Bake for 8-10 minutes, just until the edges are golden and the marshmallows start to puff up. Keep an eye on them—over-baking will make the cookies crunchy rather than chewy.
Let the cookies cool on the baking sheet for 4-5 minutes before transferring them to a wire rack to finish cooling. This also gives the marshmallows time to firm up. Store any leftovers in an airtight container for up to 3 days, though they’ll likely disappear before then!