Peanut Butter Sheet Cake (It's a winner...literally!)

I made this sheet cake for a baking contest today.  It turned out sooooo good!  Apparently the judges agreed, because I won!  This is a super-easy cake to make, but tastes divine!

Peanut Butter Sheet Cake

Ingredients

Cake:
• 1/4 cup creamy peanut butter
• 1 cup water
• 1/2 cup butter
• 1 cup sugar
• 1 cup brown sugar
• 2 cups flour
• 1 teaspoon salt
• 1 teaspoon baking soda
• 2 eggs
• 1/2 cup buttermilk
• 1 teaspoon vanilla
 
Frosting:
• 3/4 cup butter
• 6 Tablespoon buttermilk
• 1/2 cup peanut butter
• 3 1/2 cups powdered sugar
• 1 Tablespoon vanilla

Instructions

1. Preheat oven to 375 degrees.
2. For the cake: In a medium pot add the peanut butter, water, and butter and bring to a boil. Remove from heat.
3. In a separate bowl, mix together the sugar, brown sugar, flour, salt, and baking soda with a fork. Add to the peanut butter mixture.
4. Add the eggs, buttermilk, and vanilla to the bowl and mix well.
5. Stir well and pour into greased or parchment lined cookie sheet pan with a little edge (12X17 jellyroll pan). Bake for 15 minutes at 375 degrees.
6. For the Frosting: In a small pot bring the butter, buttermilk, and peanut butter to a boil. Remove pan from the heat and add the powdered sugar and vanilla. Pour frosting over the warm cake.

Source:   http://www.the-girl-who-ate-everything.com/2010/03/how-you-can-get-pregnant-from-eating.html