1.In A Large Skillet Over Medium Heat, Melt The Butter And Heat The Olive Oil. Cut The Mushroom Caps In Half, And Slice 1/4 Inch Thick. Cook Mushrooms In The Skillet 8 Minutes, Or Until Tender And Lightly Browned. Season With Salt. Stir In The Chicken Broth And Boursin Cheese. Reduce Heat And Simmer, Stirring Constantly, Until Well Blended. 2.Bring A Large Pot Of Lightly Salted Water To A Boil. Add Shell Pasta And Cook For 5 Minutes. Place The Asparagus Into The Pot, And Continue Cooking 5 Minutes, Until The Pasta Is Al Dente And The Asparagus Is Tender; Drain. Toss With The Mushroom Sauce To Serve.