Preheat your oven to 350°F (175°C). Grease an 8x8-inch square pan and set it aside for later. In a medium-sized bowl, whisk together the unsweetened cocoa powder, all-purpose flour, salt, and baking powder until well combined.

In a large bowl, combine the melted and slightly cooled unsalted butter with the granulated sugar, eggs, and vanilla extract, mixing until smooth. Gently fold the dry ingredients from Step 1 into the wet mixture until just combined, being careful not to overmix. Add the semi-sweet chocolate chunks and stir to incorporate evenly. Spread the batter into your prepared baking pan.

Bake the brownie batter in the preheated oven for about 30 minutes, or until a toothpick inserted in the center comes out with only a few moist crumbs. Remove the pan from the oven and allow the brownies to cool completely before slicing them into 9 even squares. Set the brownie pieces aside.

Line your countertop with parchment paper and arrange the cooled brownie squares on it, leaving some space between each. Melt the orange candy melts according to the package directions. Using dipping forks or toothpicks, dip one marshmallow into the melted orange candy coating—do not shake off excess coating—then quickly set it on the center of a brownie square. Gently tap the brownie on the countertop to allow the excess coating to smooth out and flow down onto the brownie. If needed, add more coating on top of the marshmallow before tapping. As a personal touch, I always make sure to use a bit extra orange coating for a more dramatic pumpkin 'drip' effect.

Quickly, before the orange candy coating sets, place a semisweet chocolate chip on top of each marshmallow to create the 'stem' of your jack-o-lantern. Repeat until all brownies are topped. Allow the candy coating to harden completely, which should take about 30 minutes.

In a small bowl, melt the remaining semisweet chocolate chips according to package directions. Transfer the melted chocolate to a piping bag fitted with a round tip or use a plastic baggie with a small tip cut off. Pipe jack-o-lantern faces onto the orange marshmallow-topped brownies. Let the chocolate harden, about 15 minutes. I like to have fun with different expressions for each pumpkin – it’s a great chance to get creative!