Preheat the oven to 350 degrees F.
In a medium saucepan over medium-low heat, melt the chocolate with the butter, stirring occasionally. Set aside.
In a large bowl, whisk together the eggs and both sugars. Stir in the melted chocolate and butter. Stir in the vanilla.
In a separate bowl, combine the flour, baking soda, and cinnamon. Stir the flour mixture into the chocolate mixture until well combined.
Grease a 13 by 9-inch pan with nonstick cooking spray or the tablespoon of butter. Pour the batter into the pan and bake for 30 to 40 minutes, until a toothpick comes out clean. Let the brownies cool to room temperature before cutting into 3-inch squares.
Recipe courtesy of Debra Ponzek and Geralyn Delaney Graham, "The Summer House Cookbook", Potter, 2003