At the Ivy you can have this dish either ready-made or you can ask for an egg yolk to be served on the side for you to add to it yourself. If you’re making it at home, I think the more you leave to your guests’ individual taste the better. Some like it hot, some don’t; some prefer it with onion, others without. Personally, I like to put in an anchovy. Whatever your preference, though, the one essential in this dish is the very best beef.