Peanut Butter Sheet Cake

INGREDIENTS

• 2 cups all-purpose flour
• 2 cups white sugar
• 1/2 teaspoon baking soda
• 1/4 teaspoon salt
• 1 cup water
• 3/4 cup butter or margarine, softened
• 1/2 cup peanut butter
• 1/4 cup vegetable oil
• 2 eggs
• 1/2 cup buttermilk
• 1 teaspoon vanilla extract
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• 2/3 cup white sugar
• 1/3 cup evaporated milk
• 1 tablespoon butter or margarine
• 1/3 cup chunky peanut butter
• 1/3 cup miniature marshmallows
• 1/2 teaspoon vanilla extract