Oriental Chicken Casserole

Another recipe of my Mom's.

1/4 cup margarine or butter
2 cups sliced celery
2 med. carrots, sliced
1 lg. onion, chopped
1 cup water
1 tsp. instant bouillon
3 cups cubed, cooked chicken or turkey
3 Tbsp. corn starch
1 Tbsp. soy sauce
1/2 tsp. salt
10 oz. frozen peas
1 4oz. can mushroom stems and pcs.
Melt butter in 2 qt. casserole. Layer celery, carrots, and onions. Microwave, covered, 8 - 10 minutes or until vegetables are just tender. Stir in remaining ingredients. Mix well. Bake at 350 degrees for 1 hour.