Preheat oven to 350 F. Grease a 9x9-inch metal baking dish; set aside.
In a large saucepan, melt butter and chocoalte together over low heat, stirring frequently.
Remove from heat, and whisk in molasses and sugars.
Whisk in eggs until combined.
Add flour, salt, cinnamon, and ginger; whisk until just incorporated.
Pour into prepared pan.
Bake for 20-30 minutes, or until a wooden toothpick inserted in the center comes out with just a few fudgy crumbs.
Let cool in pan, and serve dusted with powdered sugar, if desired.
Video
Notes
Butter - I use salted butter in this recipe. If using unsalted butter, add an extra pinch of salt.
Bittersweet chocolate - I recommend using baking chocolate, not chocolate chips as chocolate chips can have ingredients that prevent melting.
Molasses - Robust, regular, or light molasses will work in this recipe. I don't recommend using blackstrap as it can be bitter.
Brown sugar - Dark brown sugar is preferable, but light brown sugar will also work.
All-purpose flour - It's important to use a light touch with the flour when making brownies. To properly measure the flour, either weigh it or sift/stir it to break it up. Lightly spoon it into the measuring cup and level.