Blanch celery by putting in boiling salted water for about 5 minutes, then drain well.
Heat butter in oven-proof casserole dish and add carrots and onions and cook for about 5 minutes. Add drained celery and chicken broth. Sprinkle with celery seeds, salt and pepper. Place casserole in the oven and bake, covered for 30 minutes or until celery is tender. Transfer vegetables to serving dish with slotted spoon.
