Light the grill. Place the ground pork, beef, egg and breadcrumbs in a bowl. Season with salt (in moderation) and pepper and combine with your hands. Divide the mixture equally into 8 and roll into balls. Form patties by pressing the mixture between 2 layers of plastic wrap. Set aside.
2. Slice the tomatoes and grill them for 2 min., turning once.
3. Halve the bread buns and grill the cut sides for 2 min. or until nicely browned.
4. Remove and discard the plastic wrap from the burgers and grill for 6 min., or until thoroughly cooked, turning once.
5. Cut the mozzarella into 16 slices. Sprinkle the grilled side of the buns with olive oil. Place the arugula onto the bottom half of the buns, followed by a burger, 2 slices of tomato, 2 slices of mozzarella and a few basil leaves. Repeat the process to create a second layer. Cover with top half of buns. If necessary use a wooden skewer to secure the tops.
673 calories, 40g fat, 15g saturated fat, 189mg cholesterol, 694mg sodium, 28g carbohydrate, 3g fiber, 9g sugars, 46g protein