1 tbsp. butter
1/4 c. chopped onion
1/2 c. chopped celery
1 can cream of mushroom soup
1/2 c. mayonnaise
1 can (6.5 oz.) tuna, drained and flaked
2 c. cooked egg noodles
1/4 c. crushed potato chips

Place butter, onion and celery in 1 1/2 quart glass casserole. Microwave for about 3 minutes on high or until partly cooked. Stir in remaining ingredients except chips. Sprinkle potato chips (crushed) on top). Microwave on Roast or Medium for another 8 minutes or until hot all the way through. Let it stand 5 minutes before serving.