Find recipes for Chicken Tetrazzini and other Course recipes. Get all the best recipes at . Recipe directions: In a Dutch oven, saute green pepper and onion in butter until crisp-tender. Stir in flour, garlic powder and pepper until blended. Gradually add milk. Bring to a boil. Cook and stir for 2 minutes or until thickened. Stir in soup, cheeses and chicken; cook and stir until cheese is melted. Stir in peas, pimientos and spaghetti.