Preheat your oven to 350°F (175°C).
In a large bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy.
Add the pumpkin puree, egg, and vanilla extract to the creamed mixture, mixing until fully combined.
In a separate bowl, whisk together the flour, baking soda, salt, cinnamon, and chocolate chips.
Gradually add the dry mixture to the wet mixture, stirring gently until just combined.
Fold in the mini marshmallows to the cookie batter, ensuring they are evenly distributed.
Drop tablespoon-sized portions of the dough onto a prepared baking sheet, leaving space for spreading.
Bake in the preheated oven for 10-12 minutes, until the edges are lightly golden.
Remove from the oven and let the cookies cool on the baking sheet for 5 minutes before transferring to a wire rack.
Enjoy the cookies warm or store them in an airtight container for later.