For the chutney: Bring the apples, onion, apple juice, vinegar, maple syrup and thyme to a boil over medium-high heat in a medium saucepan. Reduce the heat and simmer until the liquid has almost evaporated and the apples are soft, about 45 minutes. Cool and season with salt and pepper. The chutney can be made 1 day in advance.
For the burgers: In a large bowl, combine the cheese, pancetta, apple, garlic, parsley, thyme, salt and pepper. Add the pork and mix well. Form the mixture into 6 burgers, each 4 1/2-inch in diameter and 3/4-inch thick.
Place a grill pan over medium heat or preheat a gas or charcoal grill. Oil the grill with vegetable oil cooking spray. Drizzle the burgers with oil. Cook on low heat until cooked through, for 10 minutes on each side. The burgers are also ready when a meat thermometer registers 160 degrees F when inserted into the side of the burgers. Allow the burgers to rest for 10 minutes.
Place the burgers on buns and top with chutney. Serve with lettuce leaves and sliced tomatoes if desired.
The burgers can also be cooked over low heat for 10 minutes on each side in a nonstick skillet or on a nonstick griddle.