1. Preheat oven to 350 degrees Fahrenheit (180 degrees Celsius).
2. Beat together sugars and oil.
3. Add remaining ingredients, aside from chocolate, one at a time.
4. Stir in half the chopped chocolate. Spread batter into a 9×13-inch (23×33-cm) pan and sprinkle with remaining chopped chocolate squares.
5. Bake for about 50 minutes, or until toothpick inserted comes out clean. Do not overbake.
6. Cool and cut into triangles or squares.