Herbed Chicken and Apple Burgers

Name: Herbed Chicken and Apple Burgers
Prep time: 20 min
Cook time: 20 min
Total time: 40 min
Cuisine: American
Ingredients: 1 lb ground chicken; 1 large red onion (finely chopped); 1/4 cup plain dry bread crumbs; 2 large green apples (such as Granny Smith (for a tart taste) or Golden Delicious (for a sweet taste), peeled and coarsely grated); 1 tbsp fresh sage leaves (chopped); 1 tbsp fresh thyme leaves; 1/4 tsp salt; 1/4 tsp Freshly ground black pepper; 1/4 cup Dijon mustard; 1 tbsp honey; 4 whole-wheat hamburger buns (split); 6 tbsp watercress sprigs (large stalks discarded)