Place 1/2 of chilies in bottom of greased casserole dish, cover with all of cheddar cheese. Top with rest of chilies. Cover with all of jack cheese. Beat egg whites until stiff. Beat yolks with flour, milk, salt and pepper in large bowl. Fold egg whites into yolk mixture. Pour over casserole. Bake in 325 Dutch oven for 45 minutes or until knife inserted in center comes out clean.