Directions

1. Heat the oven to 350 degrees F. Grease and flour two 8-inch baking pans; set aside.
2. In a large mixer bowl add vegetable oil, egg, and 2 teaspoons vanilla extract. Beat at medium speed until well mixed (1 minute). Add brown sugar and granulated sugar; continue beating, scraping bowl often, until well mixed (1 minute). Add the melted chocolate. Continue beating, scraping bowl often, until well mixed (1 minute).
3. In small bowl stir together flour, 2/3 cup unsweetened cocoa powder, baking soda, and salt. Add the flour mixture to chocolate mixture alternately with water, beating well after each addition. Add 1 cup sour cream; mix well. Pour into prepared pans and bake until a wooden toothpick inserted in center of cakes comes out clean (about 30 to 35 minutes). Remove cakes from the oven; cool 10 minutes. Remove the cakes from the pans; cool completely.
4. Meanwhile, in medium bowl add 1/2 cup softened butter; beat at high speed until creamy (1 to 2 minutes). Add 2/3 cup cocoa powder and 1 teaspoon vanilla; continue beating, scraping bowl often, until mixture is creamy (1 to 2 minutes). Add the powdered sugar, 1 cup at a time, beating well after each addition. Add the milk and 1/4 cup sour cream; continue beating, scraping bowl often, until creamy (1 to 2 minutes).
5. Place one cake, flat side up, on the bottom of a serving plate. Place about 1 cup frosting in the center of the cake. Spread to about 1/2-inch from the edge of the cake. Place the second cake, flat side up, on top of the frosted first layer. Frost the sides and top of cake with remaining frosting. Garnish if desired.