01 - Butterfly the chicken breasts to create four thin fillets.
02 - In a bowl, combine olive oil, minced garlic, oregano, salt, and pepper. Add chicken, turning to coat well. Marinate for 10 minutes at room temperature.
03 - While chicken marinates, mix mayonnaise, garlic, lemon juice, and salt in a small bowl to make the garlic mayo. Set aside.
04 - Heat a grill pan or skillet over medium-high heat. Grill chicken fillets for 4–5 minutes per side, until cooked through and golden. Add cheese slices during the last minute, if using, to melt.
05 - Spread garlic mayo on both halves of each toasted bun.
06 - Layer lettuce, tomato slices, and grilled garlic chicken onto the bottom halves. Top with the other bun half.
07 - Serve warm.