In a large bowl, combine dark brown sugar, finely ground white pepper, rice flour, salt, grated garlic, soy sauce, vinegar, and unsweetened pineapple juice. Mix well until the sugar has dissolved.

Thinly slice the skinless chicken thigh fillet and add it directly to the bowl with the marinade. Massage the mixture into the chicken pieces.

Cover the bowl and refrigerate for at least 1 hour, or up to 24 hours for deeper flavor.

Transfer the chicken and marinade into a large skillet. Add enough water to cover the chicken partially and bring to a simmer over medium-high heat.

Let it cook uncovered for 15-20 minutes until the liquid has reduced significantly.

Lower the heat, add oil to the skillet, and sauté the chicken for an additional 5-10 minutes until lightly charred.

Remove from heat and serve hot over freshly cooked rice.