Prepare the Pan: Preheat the oven to 350°F and line an 8-inch square baking pan with parchment paper, leaving some parchment overhanging the sides so the baked brownies can be lifted out easily.
Melt the Chocolate: Place the butter pieces and chopped milk chocolate in a microwave-safe bowl. Microwave in 30-second intervals, stirring between each interval, until the mixture is completely melted and smooth.
Add the Sugars: Stir the granulated sugar and packed brown sugar into the melted chocolate mixture until incorporated.
Incorporate the Eggs: Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
Combine the Dry Ingredients: Sift the all-purpose flour, unsweetened cocoa powder, and salt together to remove lumps and distribute the dry ingredients evenly.
Make the Batter: Gradually fold the sifted dry ingredients into the chocolate mixture using a spatula. Mix only until the ingredients are combined, taking care not to overmix.
Add the Chocolate Chips: Fold ½ cup of the milk chocolate chips into the brownie batter, distributing them throughout.
Fill the Pan: Transfer the batter to the prepared baking pan and spread it evenly. Sprinkle the remaining ¼ cup of milk chocolate chips over the surface.
Bake the Brownies: Place the pan in the preheated 350°F oven and bake for 22–25 minutes. The brownies are ready when a toothpick inserted into the center comes out with a few moist crumbs. Avoid overbaking so the brownies retain their fudgy texture.
Cool the Brownies: Let the brownies cool in the pan on a wire rack before using the parchment overhang to lift them out.
Slice and Serve: Cut the cooled brownies into 16 squares and serve.
