Over an open flame or under the broiler, char the peppers all over. Cover and cool enough to handle. Peel and seed the peppers, then puree 3 of them with 1 cup of the stock in a food processor. Dice the remaining 2 peppers into bite-size pieces and reserve for later use.
Heat the oil in a soup pot over medium-high heat, add the potatoes and chile powder, and then season with salt and pepper. Cook until the potatoes start to brown, 2 to 3 minutes. Then add the garlic and onions, and cook to tender, 7 to 8 minutes more. Add the coffee, Worcestershire, sugar, bay leaf, cinnamon, the remaining 3 cups stock, the pureed peppers and the chopped peppers.
Pour the boiling water over the masa and stir, then add to stew. Add the turkey to the stew and simmer to thicken.
Serve the stew in shallow bowls.
Place the buttermilk, Sriracha, salt, peppercorns, garlic, lemon, chives, dill and parsley in a double-bagged 2 1/2-gallon plastic resealable bag. Add the turkey breasts and refrigerate on the bottom shelf of the fridge overnight.
Preheat the oven to 325 degrees F.
Arrange a metal rack over or in a rimmed baking sheet and rub the rack with oil. Remove turkey breasts from the brine and pat them dry. Arrange the breasts on the prepared baking rack and coat the skin with a little oil, sprinkle with poultry seasoning and cook until a thermometer reads 165 degrees F and the skin is light to medium golden brown, 45 minutes to 1 hour.