
To prepare the chicken, bring a large pot of water to a boil. Add the teaspoon of salt, the white onion quarters, and the whole garlic cloves. Place the chicken breasts in the water and simmer until cooked through. Transfer the chicken to a platter and let it cool. Discard the cooking liquid and anything left in it.
When the chicken is cool enough to handle, use two forks to shred it into thin pieces. Set aside while you prepare the sauce.
In a large skillet, heat the canola or olive oil over medium heat. Add the sliced onions and garlic. Sauté, stirring often, until the onions are translucent. Keep the onions in the pan while preparing the tomato chipotle sauce.
In a blender, combine the chopped tomatoes, tomato paste, diced chipotle peppers, 1 tablespoon adobo sauce, ¾ cup water, salt, pepper, oregano, and thyme. Pulse to create a chunky sauce. Taste the sauce and adjust the seasoning as needed. Feel free to add more chipotles and adobo sauce if you want more heat! If the sauce is too thick, add a little more water.
Pour the sauce over the onions. Turn the heat down to medium low and simmer the sauce for 5 to 6 minutes to thicken. Add the shredded chicken. Stir gently to coat the chicken. Your spicy chicken tinga is ready to serve!