In a large bowl, combine the first nine ingredients; beat on low speed for 30 seconds. Beat on medium for 2 minutes. Pour into two greased and floured 8-in. baking pans. Bake at 350° for 38-43 minutes or until a toothpick inserted comes out clean. Cool 10 minutes before removing from pans to wire racks to cool completely.

Frosting  In a microwave, melt chocolate; stir until smooth. Cool to room temperature, 20-30 minutes. Meanwhile, dissolve cocoa in boiling water; cool. In a large bowl, beat butter and powdered sugar until fluffy. Add melted chocolate; beat on low speed until combined, scraping sides of the bowl as needed. Beat in cocoa mixture.

Place one cake layer on a serving plate; spread with 1 1/2 cups frosting. Top with remaining cake layer. Spread remaining frosting over top and sides of cake.