Direction :

1. Preheat the oven to 350ºF.
2. Place the sugar, brown sugar, and molasses in a large bowl. Pour the melted butter over the top and whisk to combine. Add the egg, and whisk again. 
3. Add the baking soda, cinnamon, ginger, nutmeg, and salt, and whisk to incorporate. 
4. Finally, add the flour and use a spatula to incorporate — the batter will feel more like a thick dough and it will require some elbow grease to incorporate. This is normal. 
5. Press the dough into an ungreased 9×13-inch glass or metal baking dish.
6. Transfer to the oven and bake for 22-24 minutes. The mixture will puff in the oven, but will collapse upon cooling. I like to err on the side of underbaking, and I find these are consistently done at 22-23 minutes. (If you are using a metal pan, start checking even earlier — Julie bakes them for 17-20 minutes, but she is using a larger pan, so her bars are slightly thinner.) Remove the pan from the oven and transfer to a cooling rack. Let cool for roughly 1 hour before cutting. 
7. Cut into 24 or 48 pieces. I like to make a 6×4 grid of bars; then cut each of those bars in half to make 48 pieces. 
8. Store at room temperature in an airtight container for up to 3 days (maybe longer, but chances are these bars will never make it that long.)