Preheat the oven to 375 degrees F/190C. Grease and flour a 9 x 12 baking pan
Sift the flour, salt, baking soda, baking powder, cinnamon, and nutmeg together into a large mixing bowl.
Add the butter, brown sugar, granulated sugar, eggs, vanilla, and rolled oats. Mix until combined. Fold in 1 cup of chocolate chips and spread evenly into the pan. Sprinkle with remaining chocolate chips.
Bake 30 minutes. After 30 minutes, give the pan a little shake. If it jiggles in the middle, put the pan back in and try again every 5 minutes until there is no longer any jiggle.
Remove from the oven and let cool 10 minutes before cutting. Best served warm, but great cooled as well.
For a more even look, use an offset spatula to spread the dough evenly into the pan.
For a more professional looking slice cool the cookie bars completely before slicing. You can also chill in the refrigerator to fully set before slicing. Chilled bars cut cleaner.
Use a ruler for your first slice to make the straightest possible cut.
I recommend using a wooden spoon instead of a mixer in this recipe to avoid over mixing, which will result in a tougher bar.