Minestra di quadrucci in brodo di pesce

• 1 small white onion
• 1 small leek
• 1 small celery rib
• leaves

Chop together (not too finely) the onion, leek, celery, and thyme leaves. Put in a large saucepan with the bay leaf and butter and sweat over low heat for about 15 minutes, or until the vegetables are completely wilted. Meanwhile, pour 4 cups (1