In a bowl, combine the chicken pieces with 2 tablespoons of fish sauce, half of the julienned ginger, half of the minced garlic, half of the sliced shallots, and half of the bird's eye chilli (if using). Mix well and let it marinate for at least 15 minutes at room temperature, or up to several hours in the refrigerator.

Heat vegetable oil in a large skillet or Dutch oven over medium heat. Add the remaining ginger, garlic, and shallots and sauté until fragrant, about 1-2 minutes.

In a separate small saucepan, combine granulated sugar and 2 tablespoons of water. Cook over medium-low heat without stirring until the sugar dissolves and turns into a deep amber caramel. Do not burn. Immediately pour the caramel into the skillet with the aromatics and stir quickly. Be careful as it will bubble vigorously.

Add the marinated chicken to the skillet, stirring to coat with the caramel and aromatics. Cook for 5-7 minutes, turning occasionally, until the chicken is lightly browned.

Pour in the chicken broth or water and the remaining 1 tablespoon of fish sauce. Bring to a simmer, then reduce heat to low, cover, and let it cook for 20-25 minutes, or until the chicken is tender and cooked through, and the sauce has thickened slightly.

Remove the lid and increase heat to medium-high. Simmer for another 5-10 minutes, stirring occasionally, until the sauce reduces to a desired consistency, coating the chicken nicely. Stir in the remaining bird's eye chilli (if desired) and freshly ground black pepper.

Serve hot with steamed jasmine rice and a sprinkle of fresh herbs like cilantro or scallions.