Retain 1 cup broth for later. Meanwhile, heat butter in panand add garlic, chicken, soups, pesto, sour cream, broth (from above), and mushrooms. Mix together and cook until warm, stirring often. Drain pasta when cooked, return to pan and add sauce mixture. Pour into deep 9" x 13" roasting pan, sprinkle cheese on top. Cover with foil or lid and bake 325° - 15-20 minutes. You want it hot and cheese melted, don't overcook.
Should feed 6-8 people.