Bring butter, sugar, and evaporated milk to a boil in a saucepan over medium heat. Boil for 5 to 7 minutes, then remove from heat and quickly stir in the marshmallow cream, chocolate candy, and chocolate chips, until the chocolate has melted and is fully incorporated. Pour chocolate mixture into the prepared baking pan. Dot the top of the fudge with peanut butter. Swirl a knife through the fudge and peanut butter to create a marble effect. Cover and refrigerate until firm, about 1 hour. Cut into squares for serving.