1. For the tongue: Put tongue, celery, onion, and garlic cloves into a stockpot, cover with water, and bring to a boil, partially covered. Simmer tongue, partially covered, over medium heat until tender, 4—5 hours. Drain, discarding vegetables. Let tongue rest until just cool enough to handle, then peel off skin and trim off any fat, gristle, and bones. Trim off thick meaty back part of tongue and save for another use. Cover tongue and refrigerate until cold.