Prepare pastry; set aside. Cook peas and carrots according to package directions; drain. In a saucepan cook onion and mushrooms in butter or margarine till tender. Stir in flour, salt, sage, marjoram or thyme and pepper. Add chicken broth and milk all at once. Cook and stir till thickened and bubbly. Stir in drained peas and carrots, chicken or turkey, parsley, and pimiento; heat till bubbly. Pour chicken mixture into six 10 ounce round casseroles (or use a 12 X 7 1/2 X 2" baking dish).
Roll pastry into a 15 X 10" rectangle. Cut into six 5" circles and place atop the 10 ounce casseroles. (Or, roll pastry into a 13 X 9" rectangle. Place over the 12 X 7 1/2 X 2" baking dish). Flute edges of pastry and cut slits in the top for steam to excape. Bake in a 450F degree oven for 12-15 minutes or till pastry is golden brown.
Biscuit-Topped Chicken Potpies: Prepare as above, except omit pastry. Cut 1 package (6) refrigerated biscuits into quarters and arrange atop bubbly chicken mixture in casseroles or baking dish. Bake in a 400F degree oven about 15 minutes or till biscuits are golden.