Preheat oven to 350°.
In a large sauce pan, cook carrots in ½ cup boiling salted water, covered, 5-7 minutes or until crisp tender. Drain, reserving ¼ cup of the carrot liquid. Spread carrots in a 12 x 7½ x 2″ baking dish.
In a small bowl combine mayonnaise, onion, horseradish, lemon juice, salt, pepper and reserved carrot liquid. Pour mixture over carrots. Sprinkle with Panko or other dried breadcrumbs, then drizzle with butter.
Bake for 15-20 minutes or until heated through.
From Heart and Soul: Stirring Recipes from Memphis (1992), page 220.