In a medium bowl, whisk together brown sugar, soy sauce, minced garlic, grated ginger, lime juice, and olive oil until well combined. Place the boneless chicken breasts or thighs into a resealable bag or dish and pour the marinade over the chicken, ensuring it is well coated. Allow to marinate for at least 30 minutes, or up to 2 hours for optimal flavor.

Preheat your oven to 400°F (205°C) if baking, or heat your grill to medium-high. After marinating, let the chicken sit at room temperature for about 10 minutes.

For grilling, place the chicken on the grill and cook each side for about 6-8 minutes or until the internal temperature reaches 165°F (74°C). If baking, arrange the chicken in a lined baking dish, pour any remaining marinade over, and bake for approximately 30 minutes until fully cooked.

While the chicken is cooking, sauté pineapple chunks in a skillet over medium heat for 5-7 minutes until caramelized and tender.

Taste the sauce or marinade after the chicken is cooked. Adjust sweetness with lime juice or soy sauce as necessary, and stir in chili flakes if desired.

Remove the chicken from the oven or grill and let it rest for a few minutes before slicing. Plate the chicken, spoon sautéed pineapple on top, and garnish with freshly chopped cilantro.