Cook 1 cup butter and 1/3 cup cocoa in saucepan on low heat, stirring often, until butter melts. Remove from heat. Combine sugar, flour and salt in large bowl and beat until blended -- add eggs and vanilla, beat until blended. Blend in the cocoa mixture. Spread mixure in a 8x8 square pan. Bake at 350 degrees for 20 minutes until toothpick comes out clean. Remove lid from peanut butter jar and microwave on medium for 2 minutes -- stir once. Spread melted peanut butter over warm brownies. Chill 30 minutes. Cook remaining 1/2 cup butter. 1/3 cup milk and marshmallow in large pan over medium heat - stir often until melted. Remove from heat and whisk in 1/4 cup cocoa. Stir in 10x sugar until smooth. Spread over peanut butter. Chill 20 minutes and then cut into squares.