Directions

  1. Prepare outdoor grill for direct grilling over medium-high heat; line rimmed baking pan with parchment paper. Pulse mushrooms in a food processor until small pieces remain; transfer to a large bowl. Gently mix in chicken, garlic, egg, soy sauce and salt; form into 4 (½-inch-thick) patties, place on prepared pan and freeze 30 minutes.
  2. Spray patties with nonstick cooking spray; place on hot grill rack, cover and cook 15 minutes or until browned and internal temperature reaches 165°F, turning once.
  3. Spread top buns with mustard; spread bottom buns with mayonnaise. Serve burgers in buns topped with tomato, onion and arugula.