In a medium bowl combine flour, baking powder, and salt. In a large bowl cream together white and brown sugar, butter, and vanilla extract. Add the egg and mix well. Add to dry ingredients all at once and stir until dry ingredients are moistened (batter will be slightly lumpy). Stir in 1½ cup of chocolate chips.
Fill cups 2/3 full. Top muffins with remaining chocolate chips.
Bake for 18 minutes or until toothpick inserted into the center comes out clean. Cool 1 minute before removing from pan.