Preheat the oven to 375F. In a large bowl, stir or whisk together the flour, cocoa, baking soda, cinnamon (if using) and salt. If you like, toss in the chocolate chips.
In another bowl, whisk together the eggs, sugars, oil, ginger and vanilla. Add to the dry ingredients and stir (you may need to get in there with your hands) until you have a stiff, dark dough.
Scoop out the dough by the 1/4 cupful and place a couple inches apart on a greased or parchment-lined sheet. Sprinkle with coarse salt or sugar, if you like. Bake for 15 minutes, or until cracked and set but still soft in the middle. Transfer to a wire rack to cool.
Serving Size Makes 1 dozen big cookies.