Replace the water with strongly brewed coffee for an extra special kick. Also, to create an extra fudgy cake, poke holes in the warm cake just before pouring the icing. The icing will nestle down into the warm cake creating a signature fudgy layer of deliciousness!
Preheat oven to 350°.
To prepare the cake, coat a 15 x 10-inch jelly-roll pan with cooking spray, and dust with 2 teaspoons flour. Set prepared pan aside.
Lightly spoon flour into dry measuring cups; level with a knife. Combine 2 cups flour , sugar, and salt in a large mixing bowl and stir well with a whisk. In a small saucepan melt 2 sticks of butter. Add unsweetened cocoa and stir together. Add boiling water and allow mixture to boil for 30 seconds stirring well. Remove from heat, pour over flour mixture and stir lightly to cool. In a seperate small bowl, combine buttermilk, eggs and vanilla and mix well. Stir buttermilk mixture into chocolate mixture and stir to combine. Pour batter into prepared pan and bake at 350° for 20 minutes or until a wooden pick inserted in center comes out clean. Place on a wire rack.
While cake is baking, prepare icing. Melt 1 3/4 sticks butter in a medium saucepan and add unsweetened cocoa. Stir to combine and then remove from heat. Add milk and vanilla and gradually add powdered sugar mixing well. Add chopped pecans if desired and pour over hot cake. Cool completely on wire rack.