Preparation
In 4-quart casserole combine potatoes, celery, onions and oil.
Microwave on high, stirring after half the time, until onions are tender (4 to 7 minutes). Stir in broth; cover.
Microwave on high, stirring after half the time, until vegetables are tender (7 to 11 minutes).
Stir in spinach, 3 cups milk and clams; cover.
Microwave on high, stirring after half the time, until spinach is tender (9 to 12 minutes).
In small bowl combine remaining milk and flour; stir into soup.
Cover; microwave on high, stirring after half the time, until thickened (6 to 9 minutes). Stir in fish; cover.
Microwave on high, stirring after half the time, until fish flakes with a fork (2 to 4 minutes). Stir in all remaining ingredients; cover.
Microwave on high, stirring after half the time, until soup is heated through (2 to 3 minutes).