Preheat oven to 350°F. Grease a 10x15x1 inch rimmed baking sheet, or line with foil. Set aside.
Using a hand mixer or stand mixer, beat sugars and butter until sooth and creamy. Add egg and molasses and beat until combined.
In a separate bowl, combine flour, baking soda, spices and salt. Add half the dry ingredients to the wet ingredients, beating until just combined. Add the remaining dry ingredients, beating until combined (the mixture will be thick). Stir in chocolate chips.
Dump the dough into the prepared pan and use your hands to press it into an even layer. If necessary, dampen your fingers with water. Bake for 14-16 minutes (see note). If desired, you can press additional chocolate chips onto the top of the bars right after baking. Place pan on a wire rack to cool.
Notes
Cook time: You can underbake these slightly for a moist and slightly dense blondie-like bar. They are done when the top is dry and the inside feels just slightly underbaked (this was exactly 15 minutes for me). If you'd prefer, you can bake them a couple minutes longer for a bar that's more like a thick cookie.If desired, you can set aside a couple tablespoons of white chocolate chips to press onto the top of the bars right after baking. This makes the chocolate chips more visible.