Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking pan or line it with parchment paper.

Melt the cubed butter in a medium saucepan over low heat. Stir in the granulated sugar until smooth.

Cool the mixture slightly before adding the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.

Whisk together cocoa powder, all-purpose flour, baking powder, and salt in a separate bowl.

Combine the dry ingredients with the wet mixture gradually, stirring until just combined. Fold in chocolate chips if desired.

Pour the brownie batter into the prepared baking pan, spreading it evenly.

Bake in your preheated oven for 25–30 minutes. Check for doneness with a toothpick—it should have a few moist crumbs.

Cool the brownies in the pan on a wire rack for about 10–15 minutes.

Slice into squares or rectangles and enjoy warm or at room temperature.