¼ cup low-fat mayonnaise
1 teaspoon Dijon mustard 5 tablespoons finely chopped shallot, divided 1½ teaspoons finely chopped fresh thyme, divided 1 pound ground chicken ⅓ cup finely diced ham ¼ teaspoon salt ¼ teaspoon freshly ground pepper 4 slices Swiss cheese 8 small slices pumpernickel bread or 4 large slices, cut in half, toasted 12 large leaves spinach, tough stems removed
Preheat grill to medium-high (or see Stovetop Variation). Combine mayonnaise, mustard, 1 tablespoon shallot and ½ teaspoon thyme in a small bowl. Set aside. Place the remaining 4 tablespoons shallot, remaining 1 teaspoon thyme, chicken, ham, salt and pepper in a medium bowl. Gently combine without overmixing. Form into 4 patties, about ¾ inch thick. Oil the grill rack (see Tip). Grill the burgers, turning once, until an instant-read thermometer inserted in the center registers 165°F, 4 to 5 minutes per side. Top each burger with cheese and cook until melted, 1 to 2 minutes. Assemble the burgers on toasted bread with the herb mayonnaise and spinach.