Preheat the oven to 350 degrees F. In a large bowl, combine the flour, sugar, cocoa, baking soda, and salt. Add the remaining ingredients, stirring until the batter is well combined. Pour into two 9-inch round cake pans that have been coated with nonstick cooking spray and bake for 30 to 35 minutes, or until a wooden toothpick inserted in the center comes out clean. Cool slightly and remove from the pans. Frost, using the frosting recipe

Chocolate Frosting:

In a small saucepan, melt the butter over medium-low heat. Add the cocoa and stir constantly until smooth. Pour the mixutre into a medium-sized bowl and allow to cool. Add the milk and blend with an electric beater on medium speed until smooth. Add the confectioners' sugar 1 cup at a time, blending thoroughly after each addition. Add the vanilla and beat on high speed until smooth and creamy.