Preheat your oven: Set your oven to 350°F (175°C). Line an 8x8-inch metal baking pan with parchment paper or lightly grease it.
Mix butter and sugar: In a medium bowl, whisk the melted butter and granulated sugar until smooth and glossy. This helps create that crackly top.
Add eggs and vanilla: Beat in the eggs, one at a time, followed by the vanilla extract. Mix until everything is fully combined.
Stir in the cocoa powder: Add the cocoa powder and whisk until smooth. It should look dark, shiny, and thick at this point.
Add dry ingredients: Gently stir in the flour, salt, and baking powder (if using). Mix just until there are no more streaks of flour.
Fold in chocolate chips: If using, fold in the chocolate chips or chunks for extra gooey bites throughout the brownies.
Pour into pan: Pour the batter into your prepared pan and spread it out evenly with a spatula.
Bake the brownies: Bake for 30–35 minutes, or until a toothpick inserted in the center comes out with moist crumbs. Don’t overbake—you want them fudgy.
Cool before cutting: Let the brownies cool in the pan for at least 20 minutes before lifting them out and slicing into squares.