Peanut Butter Fudge Cake

I'm posting this for Jen. She got the recipe from Sister's Cafe: http://http://sisterscafe.blogspot.com/2008/09/peanut-butter-fudge-cake.html.

This picture is from Sister's Cafe, but I'm sure Maddie's was just as lovely. This is the email Jen sent me:

Madelyn made this cake today and it is pretty yummy. Very similar to
peanut butter brownies. In fact, she spread the peanut butter and
then drizzled the frosting just like when making peanut butter brownies instead
of letting the cake cool and then frosting it. Madelyn added less powdered
sugar, maybe only 2 or 3 cups, because we don't like really thick
frosting. I don't know for sure how much she added because I wasn't home
and Braden was helping her. And she cooked it in a 10x15 glass pan for
about 20 minutes. We like the cake part thinner. But I'm sure it
would still be yummy in a 9x13 pan, too.

2 cups flour
1 tsp baking soda
2 cups sugar
1 cup butter
1/4 cup cocoa (I use dutch )
1 cup water
1/2 cup buttermilk
2 large eggs, lightly beaten
1 tsp vanilla extract
1 1/2 cups creamy peanut butter
chocolate frosting

Combine first 3 ingredients in large bowl and set aside. Melt butter in a saucepan over medium heat, stir in cocoa. Add water, buttermilk, add eggs, stirring well. Cook stirring well until mixture boils. Remove from heat, add to flour mixture and stir until smooth. Stir in vanilla. Pour batter into a greased and floured 9x13 pan. Bake at 350 for 20-25 minutes or until a wooden pick inserted in center comes out clean. Cool in pan on a wire rack for 10 minutes. Carefully spread peanut butter ( I heated it in the microwave for a minute to soften it) over warm cake. Cool completely. Spread with chocolate frosting. Cut into squares. 20-25 servings.

Chocolate Frosting
1 (16oz) package powdered sugar
1/4 cup cocoa (I use dutch)
1/2 cup butter
1/3 cup buttermilk
1 tsp vanilla extract
Bring cocoa, butter and buttermilk to a boil in a small saucapn over medium heat, stirring constantly. Pour hot mixture into a bowl with the sugar, stirring until smooth. stir in vanilla.