Butter a 9"x13" pan and set aside. In a large pot melt butter and stir until evenly caramel brown and nutty smelling. Turn heat to low and add marshmallows. Stir until marshmallows are melted and remove from heat. Add rice crispies and stir until evenly coated. Butter a spoon well to keep rice crispy mixture from sticking and press brown butter rice crispy mixture evenly into buttered pan. Set aside. In a small saucepan heat cream and butter until hot but not boiling. Remove from heat and add chocolate chips. Stir until chocolate chips are melted and smooth. Spread chocolate evenly over the top of Brown Butter Rice Crispies. Place in the freezer for 15 minutes to speed the chocolate setting. Store Brown Butter Rice Crispies at room temperature.