In a mixing bowl, combine brown sugar, soy sauce, minced garlic, grated ginger, lime juice, and olive oil. Whisk together until the brown sugar is dissolved, creating a smooth marinade.

Place the boneless, skinless chicken breasts or thighs into a resealable plastic bag or shallow dish. Pour the marinade over the chicken, ensuring an even coating. Seal the bag or cover the dish, and let it marinate in the refrigerator for at least 30 minutes, or up to 2 hours.

Preheat your grill to medium heat (375°F). If baking, preheat your oven to the same temperature. For slow cooking, set your slow cooker to low or high.

Once marinated, remove the chicken from the marinade and allow excess to drip off. For grilling, cook for 6-8 minutes on each side until the internal temperature reaches 165°F.

Check the chicken's internal temperature with a meat thermometer, looking for juices that run clear.

Before serving, taste the remaining marinade and adjust the sweetness and acidity to your liking.

Allow the chicken to rest for a few minutes, then slice if desired. Garnish with fresh cilantro.