Method

• 1.
  Place beef, pancetta and 2 tablespoons pesto in a processor. Season with salt and pepper. Pulse until just combined (do not overprocess). Form mixture into 4 patties and chill while you cook the vegetables.
• 2.
  Preheat the oven to 160°C.
• 3.
  Heat a chargrill pan or barbecue over medium heat. Toss onion in a little oil and grill for 1 minute each side or until just cooked. Place in the oven to keep warm.
• 4.
  Brush tomatoes with a little oil and season, then grill for 1 minute each side. Place in the oven to keep warm.
• 5.
  Brush both sides of patties with oil. Cook on chargrill for 2-3 minutes each side until cooked through.
• 6.
  Mix remaining pesto with mayonnaise.
• 7.
  Top patties with cheese and place in oven for 1 minute or until cheese melts.
• 8.
  Spread bread-roll bases with some of the mayonnaise mixture. Top with rocket, patties, onion and tomato. Drizzle with remaining mayonnaise mixture and top with remaining bread-roll halves.