beat butter and peanut butter for 30 seconds. add sugars and beat until fluffy. add remaining ingredients, except chocolate chips, in order given. spread into 9 x 13 pan. bake at 350 degrees for 20 minutes. sprinkle with chocolate chips and let stand for 5 minutes. spread chocolate and cool. prepare icing by beating ingredients together for a drizzling consistency. drizzle over chocolate layer and cut into bars.