Boil potatoes and 1/2 tsp salt for 20-25 minutes or until tender. Melt 2 T butter in medium saucepan. Add four, salt and pepper; cookuntil bubbly. Add milk; stir well. Cook, stirring constantly, until thickened.
Coombine potatoes, hard-boiled eggs, onion, salt, and pepper in lightly greased 1 1/2 quart casserole. Add white sauce; blend lightly.
Melt remaining 1 T butter. Add bread crumbs; mix well. Sprinkly buttered crumbs over casserole. Bake at 350* F 30 minutes. Serve.