Preheat the oven to 350 degrees. Grease and flour 2-8 inch round pans. In a large bowl, beat oil, egg and vanilla for 1 minutes at medium speed, add sugars and beat 1 more minute. Add melted chocolate and beat 1 more minute.
In a small bowl, combine flour, cocoa powder, baking soda and salt. Add that to the chocolate mixture in batches, alternating with water. Beat well after each addition. Add sour cream and mix well. Pour into pans and bake 30-35 minutes. Cool for 10 minutes, then remove from pans and let them cool completely before frosting.