In a sauce pan combine the first six ingredients; bring to a boil. Reduce heat; cover and simmer for 20 minutes. Add mushrooms and celery; cover and simmer for 15 minutes or until chicken and vegetables are tender. Remove chicken and vegetables.
De-bone chicken; dice and set aside. Slice vegetables and set aside. Strain broth, reserving 2 cups. (Discard remaining broth or save for another use.) Melt margarine in a saucepan; stir in flour until smooth.
Cook and stir over medium heat until slightly thickened and bubbly. Gradually stir in cream and reserved broth; bring to a boil. Cook and stir for 2 minutes. Add poultry seasoning, salt, pepper, peas, and reserved chicken and vegetables. Pour into a 2 quart round baking dish. Set aside and keep warm. For biscuits, combine flour, baking powder, sugar, and salt.
Cut in shortening until mixture resembles coarse crumbs. Stir in milk just until mixed. On a floured surface, roll to ½ inch thickness. Cut with a 2 inch biscuit cutter. Place biscuits on top of chicken mixture. Bake at 400° for 20 minutes or until biscuits are golden brown.