1Slow Cooker: Combine everything in the slow cooker. Stir together. Cook on low for 4 hours. Remove the chicken from the cooking liquid and shred. Stir in some of the tomatoes and some juice from cooking after you shred it for added flavor.
2Instant Pot: Add everything to the Instant Pot. Close the lid and seal. For fresh chicken breasts, cook on high pressure for 10 minutes. For frozen chicken, cook on high pressure for 13 minutes. Let the pressure naturally release. Carefully open the pot and shred the chicken using two forks. Please note, the cooking time may vary slightly depending on the size of the chicken breasts. Smaller breasts cook more quickly and very large breasts may take a bit longer.
3Stovetop: When cooking on the stovetop, I like to take a different approach to ensure the chicken comes out perfectly seasoned every time. Start by poaching the chicken. Add the chicken breast in a single layer in the bottom of a large pot. Season with salt and pepper. Cover the chicken with broth or water until there is about a half an inch of liquid above the chicken. Bring to a boil and then immediately turn down to a simmer. Cover and simmer for 5 minutes. Then turn off the heat and let the chicken continue to cook, covered, for 15 minutes. Remove the chicken and chop or shred once cooled. While the chicken is cooking, make the sauce. Add the tomatoes, onions, garlic, chipotle peppers, and salt to a blender. Blend until smooth. Add this salsa to a pot and cook for 5-7 minutes over medium heat until the sauce darkens in color. Once the chicken is cooked, simply add it to the sauce and cook for 3-5 minutes for the flavors to combine.