In a bowl, combine the brown sugar, butter, eggs and vanilla just until blended.
In a separate bowl combine the flour, baking powder and salt; add that to the brown sugar mixture. Stir in chocolate chips.
Lightly grease an appropriately sized baking dish with nonstick spray. Bake at 350° until a toothpick inserted in the center comes out clean, approximately 15-20 minutes. Cool completely and cut into squares.