• Preheat oven to 375.
• Line a 10x15 baking sheet with parchment paper, or prepare with grease and flour.
• In a large mixing bowl, whisk together flour, brown sugar, cinnamon, and salt. Set aside.
• In a small bowl, combine buttermilk and baking soda. Set aside.
• In a saucepan, bring to a simmer the water, butter, and baking chocolate, until mixture is very hot and butter and chocolate are completely melted.
• To the mix of flour and sugar, add the chocolate mixture from the saucepan and the buttermilk/baking soda mixture. Give the mixture a light stir.
• Add eggs and vanilla to your mix, stirring until all is incorporated and the mixture is of even consistency with no specks of dry flour.
• Pour into prepared pan and bake for about 30 minutes, or until the edges begin to pull away from the pan, the top bounces back when pressed, or a toothpick inserted into the center comes out clean or with just a few crumbs clinging to it.
• Immediately upon removal from oven, pour icing (below) over the top. Let set and cool a few hours or overnight.

Frosting

• In a saucepan, melt together butter, unsweetened baking chocolate, and buttermilk. Bring just to a boil, whisking to make sure everything is combined. Then remove from heat and immediately whisk in vanilla and powdered sugar. Either use an electric mixer to mix in the powdered sugar or be prepared to give your arm a workout with a wire whisk, to remove all the tiny powdered sugar lumps.
• When mixture is smooth, stir in pecans, if using. Immediately pour over hot cake.