Favorite Chocolate Sheet Cake

1 cup butter, softened

2 cups sugar

4 eggs

2 teaspoons vanilla extract

2-1/4 cups cake flour

1 teaspoon baking soda

1 teaspoon salt

1 cup buttermilk

3 squares (1 ounce each) bittersweet chocolate, melted

Frosting:

1/4 cup baking cocoa

1/3 cup milk

1/2 cup butter, cubed

1 teaspoon vanilla extract

3-1/2 cups confectioners' sugar

In a large bowl, cream butter and sugar until light and fluffy. Add eggs, one at a time, beating well after each addition. Beat in vanilla. Combine the flour, baking soda and salt; add to creamed mixture alternately with buttermilk, beating well after each addition. Stir in chocolate until combined. Pour into a greased 15x10 baking pan. Bake at 350 degrees for 23-27 minutes or until a toothpick inserted near the center comes out clean. Cool on a wire rack. For frosting, in a small saucepan, bring cocoa and milk to a boil over medium heat, stirring constantly. Remove from the heat; stir in butter and vanilla until butter is melted. Whisk in confectioners' sugar until smooth. Drizzle over cake and spread quickly. Let stand until set.