1Preheat a grill to medium-high heat (400°F) or heat a grill pan over a medium heat until hot. Mix mustard and mayonnaise and set aside. Combine chicken, shallot, salt, and pepper. Form mixture into 4 patties. Rub burgers with oil. Press a deep dimple into the center of each burger (this will help it stay flat while it cooks).
2Grill burgers, turning once halfway through, until cooked all the way, about 10 minutes total. In last 3 minutes, top each burger with two slices of ham and a slice of cheese. Cover, and let cook remaining time until cheese is melted.
3Assemble burgers, spreading top bun with some of the reserved mustard mixture and a few arugula leaves.
Finding the absolute best ingredients such a big part of Chef Antoine Westermann’s culinary career and the main drive behind all of his expertly crafted dishes. His relationship with farmers and purveyors are critical to his work as a chef. While visiting one of his providers in New York, the French chef describes his efforts to find the best local ingredients for his restaurant.