If fresh chestnuts are used, slit shells on one side and cook in boiling water to cover 20 minutes. Cool, peel off shells and skin and dice coarsely. Drain and dice canned chestnuts, if used.
Cook rice in water according to package directions, using seasonings from package and adding sherry and 1 tablespoon butter. Meanwhile, melt remaining 3 tablespoons butter in skillet. Add onion, celery and parsley and cook until onion is tender but not browned. Combine rice with vegetables and chestnuts.
Makes enough for 10-pound turkey.