Chicken en cocotte is, essentially, a hands-off pot-roasted chicken. A covered Dutch oven insulates the bird from direct heat so it cooks gently, keeping the meat tender and juicy. We take the lid off partway through and crank up the oven so the bird gets some flavorful browning. Leeks placed under the chicken release their moisture, softening and sweetening into a side dish. To remove the grit that may be trapped in the leeks’ many layers, after cutting the light-colored bottoms in half lengthwise, rinse them well, keeping the layers intact. Then cut each half crosswise into 2-inch sections.