Using a mortar and pestle, pound the garlic cloves, Kosher salt and a small amount of the palm or brown sugar into a paste.
Combine garlic paste, cilantro, remaining sugar, white pepper, coriander, fish sauce, dark and regular soy sauce, ginger and lemongrass in the bowl of a food processor. Process until a rough paste is formed. Set aside.
Place the chicken into a casserole dish, large enough to fit. Rub with the marinade on all surfaces, front and back. Cover and place into the refrigerator, and marinate for at least 2 hours and up to 2 days.
After marinating, place chicken halves on a cutting board and insert two metal skewers into each chicken half, running parallel through the legs and the breasts. Rest at room temp 30 minutes to remove the chill. Salt both sides lightly with Kosher salt.
When ready to cook, preheat the grill on high, clean and oil the grill. When it’s hot, turn off half the burners and place the chicken skin-side up on the cooler side of grill for indirect cooking.
Cover the grill and cook until an instant read thermometer inserted into deepest part of breast registers 140°F, about 45 minutes. Flip the chicken, skin-side-down on hotter side of grill, cover and cook until the skin is crisp and an instant read thermometer inserted into deepest part of breast registers 145 to 150°F, about 3 minutes longer, carefully as the skin is very prone to burning. If the chicken starts to burn, slide it back to the cooler side of the grill. Transfer chicken to a cutting board and allow to rest for 5 minutes.
Meanwhile grill the Kumquats, until lightly charred on both sides.
Carve the chicken by separating the legs and thighs, the wings and breasts and finally cut each breast in two and serve with grilled kumquats and dipping sauce.
Thai Sweet Chili Dipping Sauce
Combine all ingredients in a small sealable container. Shake well, set aside, and allow sugar to dissolve, shaking every 10 minutes or so. When sugar is fully dissolved, store in refrigerator until ready to use. Sauce will keep in the refrigerator for up to 3 weeks.
Use gloves while chopping chilies and carefully scrub cutting board when finished.