The trick to this dish is to take your time. Make the marinade early so the flavors can develop. Don’t try to rush the sauce; it really needs to thicken slowly.
Make the marinade ahead. Combine all marinade ingredients (1 teaspoon fish sauce,1 teaspoon light brown sugar, curry powder, 2 cloves minced garlic, ground cumin, salt, 3 tablespoons coconut milk) and let it sit for at least an hour. You can also soak your skewers at this time. Combine all the sauce ingredients (green curry paste, paprika, 2 teaspoons minced garlic, 2 tablespoons fish sauce, peanut butter, 3 tablespoons light brown sugar, 2 cups coconut milk, lime kafir leaves, chopped peanuts) in a medium pan and simmer gently until it reduces and becomes thick. Reserve ¼ cup of the sauce for brushing on the chicken during the cooking process.
The chicken tenderloins need to be cut to half their original thickness. The easiest way to do this is to lay the tenderloin flat on a cutting board, and slice your knife sideways, cutting it in half. When you skewer the chicken, weave the skewer through the meat to create several “ripples”.
Place your skewered chicken in a shallow dish and pour the marinade over and distribute evenly. Wait 15 minutes before grilling over a medium-high heat (you could also use a grilling pan on your stove-top). Once the chicken is nearly cooked, brush one side with a little of the peanut sauce.
To serve, place on a warm platter and sprinkle with chopped fresh cilantro.