Peanut Butter Sheet Cake

My family LOVED this sheet cake! They actually fought over the last few pieces and asked me to make it again right away.
Peanut butter Sheet Cake
 2 cups flour
 2 cups sugar
 1 tsp salt
 1 tsp baking soda
**Whisk together well in a large bowl. Set off to the side.
 1/2 cup peanut butter
 1 cup water
 1 cup butter
**cook over medium-low heat. Bring to a low boil and add to the dry ingredients
 2 teaspoons vanilla extract
 2 eggs
 1/2 cup buttermilk
**Add to the the mixture and blend well with a mixer.
**Pour on to a large sheet pan that has been greased (or 2 13x9 pans)
Bake at 350ºF about 30 minutes, make sure a toothpick inserted in the middle comes out clean. Set off to the side to cool
Frosting
 ½ cup butter
 ½ cup peanut butter
 1/3 cup milk
*in a sauce pan over medium low heat, bring butter, peanut butter and milk to a low boil. Remove from heat and add:
 1 tsp vanilla
 4 cups powdered sugar
*Whisk well until all of the powdered sugar has dissolved and there are no more lumps
**Pour over the cooled cake and spread out evenly