Preheat your oven to 350°F and line your baking sheet with parchment paper or a silicone mat, this helps keep the cookies from sticking!

In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, unsweetened cocoa powder, and salt. This step is important for getting that perfect texture, so make sure everything’s well mixed before setting it aside.

In a large bowl, beat together the unsalted butter, light brown sugar, and white granulated sugar with an electric mixer on medium-high speed until it's creamy and fluffy. 

Once it’s smooth, add the eggs one at a time and then mix in the vanilla extract. Keep going until the mixture is perfectly smooth and velvety.

Now, slowly add the dry ingredients to the wet mixture, about half a cup at a time, mixing gently after each addition. Stop mixing once everything is just combined, overmixing could make the cookies too dense, and we’re aiming for soft and chewy.

Stir in most of the chocolate chips and mini marshmallows, leaving a little behind for topping. 

Give it a gentle mix to make sure the chocolate and marshmallows are evenly distributed throughout the dough.

Scoop generous dollops of dough onto your prepared baking sheets, leaving about 2 inches of space between each cookie. If you want bigger cookies, feel free to use a larger scoop, but keep in mind they may need a few extra minutes to bake.

Bake for 10-13 minutes, keeping an eye on them. You want the edges to be set, but the centers should still look a little soft. They’ll firm up as they cool, so don’t worry if they seem a bit underdone.

As soon as the cookies come out of the oven, press the reserved half-cut marshmallows into the tops and sprinkle the remaining chocolate chips over them. The heat from the cookies will melt everything just perfectly, creating a gooey, irresistible topping.

Let the cookies rest on the baking sheets for a couple of minutes before transferring them to a wire rack to cool completely. Enjoy!