Cook noodles according to package directions, omitting salt. Drain; cover. Set aside.

Melt margarine in large nonstick skillet over medium-high heat. Add mushrooms and onion; cook and stir 5 minutes or until onion is tender.

Using wire whisk, blend chicken broth, milk and flour in small bowl. Stir into mushroom mixture; bring to a boil. Cook and stir about 2 minutes or until thickened. Reduce heat to medium; stir in tuna, peas, pimiento, thyme and salt. Add noodles and pepper; mix thoroughly. (Casserole can be served at this point.)

Preheat oven to 350 degrees. Spray 2-quart casserole with nonstick cooking spray. Spread noodle mixture evenly in prepared casserole. Bake 30 minutes or until bubbly and heated through. Let stand 5 minutes before serving.

This recipe yields 6 servings.

Exchanges Per Serving: 2 Starch, 2 Meat.

Nutrition Facts: Calories 254; Calories from Fat 11%; Total Fat 3g; Saturated Fat 1g; Protein 23g; Carbohydrates 33g; Cholesterol 18mg; Sodium 585mg; Dietary Fiber 2g.