Chocolate Mayonnaise Cake

2 cups flour
1 cup sugar
1/2 cup cocoa
1 1/2 teaspoon baking powder
1 1/2 teaspoon baking soda
1 cup (+~2 tablespoons) ice water
2 teaspoons (+) real vanilla extract
1 cup real mayonnaise
Sift together flour, sugar, cocoa, baking powder and soda. Add ice water and vanilla. When mixed thoroughly, fold in mayonnaise. If you're using a mixer, fold the mayonnaise in by hand. Stir just till mixed; do not over beat. Pour into a greased and floured (or baker's joy) 13x9x2 pan and bake 30 minutes at 350 degrees. Cake is done when it starts to pull away from the sides of the pan and the top starts to crack; you can also use a toothpick test; do not overcook. Cool five minutes before removing from the pan. Butter frosting: 1 /2 stick butter 1 pound powdered sugar (dash salt) 1 /2 cup cocoa (optional) 2 tablespoons (+) milk 1 teaspoon (+) vanilla cream butter, 1/2 sugar, and salt. Add cocoa and 1 tablespoon milk. Cream. Add sugar and milk till the consistency is right and then beat at mixer's highest speed. Frost cake immediately.