Place butter in 1 1/2-qt. glass casserole.
Microwave at high setting 1 minute, or until melted.
Pour over bread crumbs, tossing to mix; set aside.
Place frozen Brussels sprouts and water in same casserole.
Cover and microwave at high setting 16 minutes, or until Brussels sprouts are tender, stirring every 5 minutes.
Drain Brussels sprouts.
Stir in mushroom soup, pimientos and thyme.
Sprinkle with buttered bread crumbs.
Microwave at high setting 4 minutes, or until hot.