Steps:

• Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 10x15 inch pan.
• Combine the flour, sugar, baking soda and salt. Beat in the sour cream and eggs. Set aside. Melt the butter on low in a saucepan, add the water and 5 tablespoons cocoa. Bring mixture to a boil then remove from heat. Allow to cool slightly, then stir cocoa mixture into the egg mixture, mixing until blended.
• Pour batter into prepared pan. Bake in the preheated oven for 20 minutes, or until a toothpick inserted into the center comes out clean.
• For the icing: In a large saucepan, combine the milk, 5 tablespoons cocoa and 1/2 cup butter. Bring to a boil, then remove from heat. Stir in the confectioners' sugar and vanilla, then fold in the nuts, mixing until blended. Spread frosting over warm cake.

Steps:

• Preheat oven to 350°. Grease a 13x9-in. baking pan., In a large bowl, whisk flour, sugar, baking soda and salt. In a small saucepan, combine water, butter, peanut butter and cocoa; bring just to a boil, stirring occasionally. Add to flour mixture, stirring just until moistened., In a small bowl, whisk eggs, sour cream and vanilla until blended; add to flour mixture, whisking constantly. Transfer to prepared pan. Bake until a toothpick inserted in center comes out clean, 25-30 minutes., Meanwhile, prepare frosting. In a large bowl, beat confectioners' sugar, peanut butter, milk and vanilla until smooth., Remove cake from oven; place pan on a wire rack. Immediately spread cake with frosting; sprinkle with peanuts. Cool completely.