2 lbs. Alaska Halibut, thawed if necessary
1/2 cup each finely chopped onions, green peppers, celery and carrots
6 Tbsp butter or margarine, divided
3 cups chicken broth
3/4 tsp salt
1/2 tsp white pepper
2 cups milk
3 Tbsp flour
2-1/2 cups shredded sharp Cheddar cheese
1 Tbsp minced parsley