I can count on the fingers of one hand the number of great chicken tacos I've had in my life, and I'd still have one finger left to point accusingly at all the people who've served me dry, bland, flavorless meat in tortillas past. See, chicken tacos don't have to be dry. Just ask the lady who serves up the incredibly juicy chicken tacos at the El Gallo Giro truck in San Francisco's Mission district, or the slow-roasted pick-it-yourself affair from the Los Potosinos truck in Columbus, OH.
There are two ways to go about making a moist and flavorful chicken taco. The first is to dry-brine white meat chicken before slow-cooking. Dry brining is a technique in which the meat is salted heavily for at least a day in advance, which alters the protein structure of the muscles in such a way that it allows the meat to retain more moisture as it cooks. The second is to skip the white meat altogether and just use chicken thighs, which remain juicy as they cook, due to their high concentration of fat and connective tissues. The latter is what we're using today.
Having recently driven through Hatch, New Mexico right at the start of Hatch chile season, I had green chile on my mind (not to mention in my fridge). For this recipe, I start with fresh Hatch chiles and a tomatillo and broil them along with onions and garlic until they are completely charred and tender. The peppers become sweet and smoky (not to mention easy to peel) and the tomatillo balances it all out with its bright acidity.
With a sauce made, I then sear chicken thighs in a hot skillet until the skin is crisp. The goal here is really just to develop some nice browned flavors, as the skin isn't going to make it into the final dish (you can pull it off and eat it at the end before shredding if you'd like). After browning, I deglaze the skillet with water (you can use chicken stock), add the salsa, then return the chicken to the pan and let it simmer until completely falling-off-the-bone tender.
The rest is pretty self explanatory: shove the meat into a tortilla, top it as desired, and cram it into the nearest willing mouth as fast as possible. If you're lucky, that'll be yours.