This dish is so popular (we sell about four hundred orders of it a week) that our cooks grumble when the first crates of Brussels sprouts roll in. They know that these tiny cabbages will soon dominate their days and nights. For this recipe, look for smaller-than-golf-ball-size sprouts that are firm and tight. Be patient and let them get a good char on the cut side, almost to the point of burning. It brings a toasty, nutty flavor that contrasts with the sweet dates and sharp vinegar. You may have to adjust the cooking time to accommodate smaller sprouts, in early winter, or the larger ones as they mature throughout the season. We generally leave very tiny ones whole and quarter the larger ones, which we do not like as much.