In A Skillet, Saute Mushrooms In Butter For 2-3 Minutes Or Until Tender. Set Aside And Keep Warm. In A Bowl, Combine The Beef And Seasonings Just Until Mixed. Shape Into Eight Thin Patties. Sprinkle Half Of The Patties With Blue Cheese; Tip With Remaining Patties And Press Edges Firmly To Seal. Grill, Uncovered, Over Medium-Hot Heat For 3 Minutes On Each Side. Brush With Some Of The Barbecue Sauce. Grill 10-12 Minutes Longer Or Until Juices Run Clear, Basting And Turning Occasionally. Drain The Mushrooms. Serve Burgers On Rolls Topped With Mushrooms.