Southerners lay claim to scalloped potatoes as if the French gratin dauphinois never existed, but it’s only recently that we’ve embraced fresh fennel as a wonderful vegetable to braise, stuff into baked fish, eat raw in salads and with dips, or use to enhance our beloved scalloped potatoes. (Of course, if, like many Southerners, you have a natural prejudice against licorice, you probably won’t like fennel, although its flavor is very light and delicate when the bulb is cooked.) Fresh fennel is now widely available throughout the winter months and keeps well, tightly wrapped, in the refrigerator for about a week. When shopping, look for crisp, unblemished bulbs, and refuse any with wilted, feathery tops. Check this dish carefully after about 40 minutes. If it appears to be baking and browning too rapidly, add a little milk around the sides and baste the potatoes and fennel well before adding the remaining cheese.