Set your oven to 350°F (175°C) and grease or line an 8x8-inch baking pan with parchment paper. This ensures your brownies come out easily without sticking.

In a medium bowl, whisk together the melted butter and sugar until smooth. Add the eggs and vanilla extract and continue whisking until fully combined.

In a separate bowl, sift together the cocoa powder, flour, salt, and baking powder. Slowly fold the dry ingredients into the wet mixture, stirring just until combined. Be careful not to overmix—it’s okay if the batter is a little thick.

For an extra dose of chocolate, fold in the chocolate chips. This step is optional but highly recommended for a richer, chocolatey experience.

Pour the brownie batter into your prepared baking pan and spread it evenly. Bake for 20-25 minutes or until a toothpick inserted into the center comes out with a few moist crumbs. Keep in mind that the brownies will continue to cook slightly after you remove them from the oven.

As soon as the brownies come out of the oven, sprinkle the mini marshmallows evenly over the top. Return the pan to the oven for another 5 minutes to allow the marshmallows to puff up and melt into the brownies. The marshmallows should be golden and gooey.

Let the brownies cool in the pan for about 10 minutes before cutting them into squares. This will help the marshmallows set just enough to hold their shape without losing that gooey texture.