Chicken and Rice Casserole

2 tbsp butter
1 med onion
1 pouch ready to serve rice (Uncle Bens)
3 cups cooked chicken
1 cup frozen peas
1 1/2 cups shredded cheddar
1 cup mayo
1 can Cream of Chicken soup
1 can sliced water chestnuts
1 jar (drained) sliced pimento
3 cups crushed ridged potato chips.

Melt butter in skillet and saute onion for 5 min. Microwave rice according to package. Combine onion, rice, chicken, peas, cheese, mayo, soup, water chestnuts, and pimento in large glass bowl. Toss gently. Spoon mixture in greases 13 by 9 pan. Top with chips.
Bake at 350 for 25 minutes.