Preheat oven to 350°F (175°C). Line an 8-inch square baking pan with parchment paper.

In a large bowl, whisk together the flour, sugar, cocoa powder, baking powder, and salt.

Add the milk, melted butter, and vanilla extract to the dry ingredients. Stir until just combined; avoid overmixing.

Fold in the chocolate chips if using. Pour the batter into the prepared pan and smooth the top with a spatula.

Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out mostly clean with a few moist crumbs.

Allow the brownies to cool in the pan on a wire rack before slicing into squares.