Preheat oven to 400 degrees.

For the cake, in a medium bowl combine the sugar and flour. In a large bowl mix the eggs, baking soda and sour cream. Set aside. In a small saucepan combine peanut butter, butter, and water. Bring to a boil. Stir the boiled mixture into the flour mixture, slowly add to sour cream mixture. Mix well. Pour into lightly greased 15 x 10 inch sheet or jelly roll pan.

Bake 20 minutes or until toothpick inserted in the center comes out clean.

For the frosting,while cake is baking, combine the butter,peanut butter and milk in a saucepan. Bring to a boil stirring constantly. Add powdered sugar and mix well. Stir in vanilla. Frosting will be thick. (I sometimes have to add another splash of milk) Pour and spread over cake while both are still warm.