Measure the flour, baking powder and salt and sift directly into the batter. Mix gently until well combined and no trace of the dry ingredients remains. Using a wooden spoon, stir in the chocolate chips. Spread the dough into the 9x9 pan with a spatula. Bake for 25 minutes or until toothpick inserted into the center comes out clean or with only crumbs, not batter, on it. Allow to cool for 1 hour before cutting.