Pat chicken breasts dry with paper towels. If breasts are thicker than 1 inch, place between two sheets of plastic wrap and gently pound to an even 3/4-inch thickness. This ensures even cooking.

In a medium bowl, whisk together balsamic vinegar, olive oil, garlic, Dijon, honey, oregano, salt, and pepper until emulsified. Taste the marinade — it should be tangy with a hint of sweetness, not harsh.

Place chicken in a zip-top bag or glass dish. Pour marinade over chicken, seal, and massage to coat. Refrigerate for at least 1 hour, up to 4 hours. Do not exceed 4 hours — the acid will begin to break down the meat's texture, making it mushy.

Remove chicken from refrigerator 20 minutes before grilling. This takes the chill off and promotes even cooking.

Preheat your grill to medium-high heat, about 400-450°F. Clean and oil the grates well to prevent sticking.

Remove chicken from marinade, letting excess drip off. Do not pat dry — the clinging oil helps prevent sticking and promotes browning.

Place chicken on the grill. Cook for 5-6 minutes on the first side without moving. You'll see the edges begin to turn opaque and small bubbles appear on the top surface. Flip once using tongs.

Cook for another 4-5 minutes. The internal temperature should reach 160°F when inserted into the thickest part of the breast. Carryover cooking will bring it to 165°F as it rests.

Transfer chicken to a cutting board and let rest, loosely tented with foil, for 5 minutes. This step is non-negotiable — it redistributes juices so they don't run out when you slice.

Slice against the grain, garnish with fresh herbs if desired, and serve.