In a large bowl, combine flour, sugar, soda and salt. Set aside. In a saucepan bring water and butter to a boil. Sit in peanur butter and oil until blended. Pour over dry ingrediants. Mix until blended. Add eggs, buttermilk and vanilla. Mix well. Lightly grease a jelly roll pan. Pour mix into pan and bake at 350 for 20-25 minutes, or until a toothpick inserted in cake comes out clean.
For glaze, combine sugar, buttermilk and peanut butter in a saucepan. Bring to a boil, stirring constantly. Remove from heat and pour over powedered sugar and vanilla. Beat until smooth. If the icing is too thick, add a splash of milk until it is smooth.
Spread over cake.
Recipe by Fencerow to Fencerow at http://www.fencerowtofencerow.com/2013/10/10/14-meals-to-a-hungry-field-crew/