Note: Buttermilk or thin yogurt may be used instead of sour milk/vinegar.

Combine softened butter and sugar until fluffy. Add eggs, one at a time, beating well after each addition. Mix in vanilla. Stir hot water into cocoa to form smooth paste and add gradually to creamed mixture. Set aside. Combine flour, baking soda, baking powder and salt; add to creamed mixture alternately with sour milk. Pour batter into two greased and floured 9 inch layer pans.

Bake at 350°F for 35 minutes or until wooden pick comes out clean. Cool 10 minutes in pans; remove to wire racks. Chill before frosting.