Put the chicken pieces in a large saucepan and cover with water. Season with salt. Cover and cook over medium to medium-high heat until no longer pink. About 20 minutes.
When the chicken is done, pour off the water (you can save it for another use!). Using two forks, shred the chicken. Alternatively, put the chicken in the bowl of your stand mixer and shred it using the paddle attachment. Works like a charm.
In a medium saucepan over medium-high heat, heat some oil, then add the onion. Saute until translucent, then add the garlic, salt, and pepper. Cook for 30-60 seconds more being careful not to brown the garlic. Add the oregano and cumin.
Stir in the water, tomato paste, chipotle peppers, and sugar. Mix well and allow it to cook just till it is a bit thick, about 5 minutes.
Pour the sauce over the shredded chicken and stir till all of the chicken is coated.
Use Chicken Tinga to make tostadas, quesadillas, enchiladas, or tacos. I use homemade corn tortillas and as toppings, I offer tomatoes (or pico de gallo), queso fresco (or cheddar cheese), cilantro, avocado slices, crema, or sour cream.