When buying Brussels sprouts, choose those with small, tight heads, no more than 1 1/2 inches in diameter, for the best flavor. Larger sprouts can often be trimmed of loose leaves along the stem and still be quite good; they cook best when cut in half. To use fresh chestnuts, place the nuts in a saucepan, cover them with boiling water, and simmer them for twenty to thirty minutes. Alternatively, roast them in a 425-degree oven for twenty to twenty-five minutes until tender. Peel both the shell and the thin skin from the meat when they are cool enough to handle. If chestnuts are unavailable, substitute half a cup of toasted chopped hazelnuts.