Step 1 Heat the oven to 325 degrees.
Step 2 Rinse the duck legs and pat them dry. Rub them all over with the herbes de Provence. Season well with salt and pepper. Spread the mustard over the skin side of each leg to coat thinly. Lay the legs in a shallow baking dish, leaving space between them. Sprinkle evenly with the panko or breadcrumbs and drizzle evenly with the melted butter.
Step 3Roast 1 1/2 to 2 hours, or until the meat is very tender and the coating is crisp. Serve on a bed of mesclun (no dressing is necessary as the duck juices and mustard will coat the salad).