Preheat the oven to 350°F (175°C). Line your metal baking dish with a parchment sling for easier removal after baking.
In a large mixing bowl, combine the eggs, white sugar, and brown sugar. Beat on high speed for about 60 seconds until the mixture lightens in color and becomes visibly thicker.
Add the melted butter and vanilla extract, mixing at medium speed until the ingredients are well combined.
Sift in the flour, cocoa powder, salt, and baking powder. Using a spatula, gently incorporate the dry ingredients into the wet until just blended. Fold in the chocolate chips if desired.
Transfer the brownie batter to the lined pan and spread into an even layer. Bake for 35–40 minutes, or until a skewer inserted near the center comes out mostly clean with a few moist crumbs. Allow the brownies to cool in the pan completely. For faster cooling, chill in the freezer for 30 minutes after they’ve reached room temperature.