1. Preheat oven to 400. Grease and flour a 13x9x2-inch baking pan. Stir together buttermilk and soda in measuring cup or small bowl and reserve for later use. Combine butter, water, oil, and cocoa in medium saucepan; bring to a boil over medium heat, stirring to melt butter.

2. Remove pan from heat and stir in buttermilk mixture.

3. Add eggs and vanilla; blend thoroughly.

4. Stir in flour, sugar, and cinnamon until blended.

5. Pour batter into prepared pan. Bake for 15 to 20 minutes or until cake begins to pull away from sides of pan and toothpick inserted in center comes out clean.

6. Cool in pan on wire rack.

7. Spread with chocolate Frosting.

8. * chocolate FROSTING: 1/2 cup) butter or margarine, 1/4 cup milk, 1/4 cup cocoa, 4 cups sifted confectioners' sugar, (about 1 pound), 1 teaspoon vanilla.

9. Combine butter, milk, and cocoa in medium saucepan.

10. Bring to a boil over medium heat, stirring to melt butter.

11. Remove from heat; gradually stir in sugar and vanilla.

12. Stir until smooth.

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