Preheat the oven to 350°F. Spray an 8x8-inch baking dish with nonstick spray, then line it with parchment paper. Allow the edges to hang over. You'll use these as handles to lift the brownies out later. Spray the parchment with nonstick spray too.
In a medium bowl, whisk together the flour, baking powder, and salt. In a large, microwave-safe bowl, heat butter and chocolate until the butter is melted. Usually, it takes 60 to 75 seconds. Whisk the butter and chocolate together until the chocolate is melted and smooth. You can heat a few more seconds if needed. (Alternately, you can melt the butter and chocolate in a pan on top of a pot of simmering water.)
Remove the butter mixture from the heat. Whisk the sugars into the mixture. Then whisk in the eggs, yolk, and vanilla. Stir in the flour mixture until well incorporated. Fold in the chocolate chips.
Pour the batter into the prepared pan and bake for 25 to 30 minutes. Bake until a skewer inserted into the center of the brownie comes out clean. Remove from the oven and cool completely before adding the glaze
For the Muddy Buddy mixture
Heat a saucepan on medium-low. Melt the butter for coating. Whisk in the cocoa powder, milk, and 1 cup of powdered sugar. Remove from the heat.
Cut the brownies into equal pieces. Drop them in the chocolate turning to coat all sides. Using 2 forks helps, you can also use a pastry brush to paint the frosting on the brownies.
Immediately drop the brownies into the 2 cups of sifted powdered sugar, turning to coat all sides. Place on a wire rack to dry. Repeat with remaining brownies.
Serve immediately or store in an airtight container until ready to store. Can be stored on the countertop.
Notes
I didn't glaze my brownies but if you want to here's the recipe.GLAZE: 2/3 cup powdered sugar 2 tablespoons unsweetened cocoa powder 1/4 teaspoon vanilla extract 4 to 5 teaspoons hot water (or more, as needed)PREPARE THE GLAZE: In a small bowl, combine the powdered sugar, cocoa and vanilla. Whisk in 4 teaspoons of hot water, then add more water- 1 teaspoon at a time- until you reach a desired glaze consistency. You want to be able to pour it on the brownies. Use the parchment paper to move the brownies from the pan to a cutting board. Pour the glaze on top of the brownies, and use the bottom of a spoon to gently spread it to the edges. Let the glaze set (chill if you'd like) before cutting.