Butter bottom and sides of a 9x13 rimmed pan; set aside. Measure krispy cereal into large mixing bowl; set aside. Place butter, peanut butter, vanilla and marshmallows in a large saucepan. Cook on low until they have completely melted, stirring often to prevent sticking. Once completely blended/smooth, remove from stove; pour immediately over krispy cereal. Stir well, to fully coat cereal. Pour mixture into buttered 9x13 pan. Press mixture down with fingers to compress; spread to cover entire pan. Let cool.
In a medium saucepan, melt butter, peanut butter, and cocoa powder until completely smooth, stirring often until smooth. Remove from heat. Stir in vanilla extract, then add powdered sugar and enough milk (approx 2-3 Tablespoons +) to make the frosting easily spreadable. Pour frosting over surface of krispy bars, then quickly spread, to fully cover.
Let frosted bars sit for a while to let frosting firm up slightly, then use a knife to cut into 24 equal sized bars. When ready, serve and ENJOY!
Chocolate Peanut Butter Krispy Bars https://www.thegratefulgirlcooks.com/chocolate-frosted-krispy-bars/