Preheat oven to 350. Butter 9 x 13 pan; set aside. Use metal blade to mix the first 6 ingredients until combined, about 5 seconds. In a 4 cup liquid measure, stir together the remaining ingredients. With the machine running, slowly pour liquid in a steady stream through the small feed tube. Let blend until smooth, about 5 seconds. Scrape down work bowl and mix 5 seconds more. Pour into prepared pan and bake for 40 to 45 minutes, or until a toothpick inserted in the center comes out clean. Remove from oven and let cool on wire rack. Frost with Dark Chocolate Frosting. Break chocolate into 1" chunks. Use metal blade to chop fine. Bring water and butter just to boil; remove from heat; add vanilla. With machine running, pour liquid in slow stream through tube. Scrape; add sugar. Blend. Shared by JEANNE SCHIFF, Prodigy ID# SSBB43A.