Season chicken with salt and pepper, saute in butter until browned.

Add onions and mushroom, continue cooking 2 minutes longer.

Stir in sherry, peas, and broth. Cover and simmer about 20 minutes.

Add tomatoes. Dissolve cornstarch in mushroom liquid (use a little of the chicken broth if using fresh mushrooms) and stir into chicken mixture. Cook, stirring frequently, about 5 minutes longer.

Serve over beds of fluffy rice. Garnish with chopped fresh parsley, if desired.