First prepare the vegetables and herbs. Remove the strings from the stick of celery and cut it in half lengthwise. Then cut the celery and carrots into julienne strips 5 cm (2 in) long. Slice the onions and shallots into rings. Prick the head of garlic here and there with the tip of a knife blade. Make a bunch with the thyme, bayleaf, sage and tarragon, wrap it in a piec