Preheat oven to 390º. Finely chop 1 long red chili (about a tbsp) and combine with ginger, garlic, oil, ½ cup cilantro, salt and pepper in a small bowl and set aside.
Rinse and pat chicken thoroughly dry. With the back of a spoon, or your fingers, start at the neck and loosen the skin from the breast meat, as far down as you can go. Just the breast, not the wings or legs/thighs.
Spoon chili/cilantro mixture under the loosened skin, and use your hands ON TOP of the skin to evenly spread it around the surface of the breast meat. Into a large dutch oven, add the chicken stock, kaffir lime leaves, lemongrass and 1 whole red chili.
Place the chicken in the stock mixture, cover, and roast for 45 minutes. Remove the lid, and add coconut milk, and potatoes. Return to oven, uncovered, and roast another 30 - 45 minutes ~ until the chicken is done, the juices run clear, and potatoes are tender.
Remove chicken from broth and tent loosely with foil. Skim any excess fat from the broth. To finish the broth, over low heat, add lime juice, coconut sugar and fish sauce, stirring to dissolve sugar. Lastly, add the rest of the chopped cilantro and combine.
Serve, either on a platter surrounded by potatoes, with the broth on the side ~ or, as I preferred, cut the chicken up into 4 to 8 pieces and return to the warm broth in the pot and then serve out of the pot.