Preheat oven to 350°F. Coat a 12 x 17 inch rimmed baking sheet with nonstick baking spray and line the bottom with parchment paper. Spray the parchment paper with nonstick baking spray. Set aside.
Whisk together the flour, baking soda, salt and spices in a medium bowl. Set aside
In the bowl of a stand mixer fitted with the paddle attachment, or in a large bowl with a handheld mixer, beat the butter and sugars on medium-high speed until creamy and fluffy (about 3 minutes)
Add in the eggs and egg yolk, one at a time, scraping down the sides of the bowl with each addition. Add vanilla and molasses and mix on medium speed until combined.
With the mixer on low speed, add the flour mixture until just combined. Do not overmix. Fold in the white chocolate chunks.
Spread the batter evenly into the prepared pan and bake until golden on the edges for about 25 minutes. Cool bars in the pan on a wire rack and then cut into 2 inch squares. Enjoy!