Preheat oven to 350°F. Line a 9x13-inch pan with aluminum foil & spray with nonstick cooking spray.

Stir together the sugar, butter, vanilla & eggs in a medium bowl. Add the flour, cocoa powder, salt & baking powder all at once & stir until just combined. Stir in half of the semisweet chocolate chips & spread the mixture in the prepared pan.

Bake until the brownies begin to pull away from the edge of the pan & set in the center (about 30 to 35 minutes). Immediately sprinkle with the remaining semisweet chocolate chips & let stand until the chips are melted (about 5 minutes). Spread the melted chips evenly over the top if the brownies with a spatula. Let the chocolate cool for about 10 minutes. Lift the brownies out of the pan with the foil & cool completely on a rack. Cut into 16 squares & serve.