01 - Butterfly the chicken breasts horizontally to create four thin, even fillets for quick and even cooking.
02 - Whisk together olive oil, minced garlic, oregano, salt, and pepper. Coat chicken thoroughly and let stand at room temperature for 10 minutes to absorb flavors.
03 - Combine mayonnaise, minced garlic, lemon juice, and salt in a small bowl. Mix until smooth and refrigerate until ready to assemble.
04 - Heat grill pan or skillet over medium-high heat. Cook chicken fillets for 4-5 minutes per side until golden brown and internal temperature reaches 165°F. Add cheese slices during final minute if desired.
05 - Lightly butter the split buns and toast in the same pan or under a broiler until golden and crispy.
06 - Spread garlic mayo generously on both bun halves. Layer crisp lettuce, ripe tomato slices, and grilled chicken on bottom buns. Crown with top bun and serve immediately.