Brown the chicken, one of two ways:
– Grill the chicken breasts on a cast iron grill pan (or a grill), 4-5 minutes per side and set aside. This is my preferred method because it adds an extra smoky flavor to the dish.
– Heat olive oil over medium heat in a dutch oven and add chicken and cook until nicely browned, about 5-6 minutes. Flip chicken breasts and continue cooking to lightly brown the other side, for about 3-4 minutes, and set aside. (Don’t worry if you have larger chicken pieces that don’t finish cooking, you will finish cooking the chicken by simmering it in sauce later on).
Once you’ve browned the chicken and set it aside, sauté the onion in a dutch oven and cook on medium heat for about 5 minutes, stirring occasionally until it’s slightly browned.
Add garlic, tomatillos, cumin, oregano, and a pinch of salt and and cook until fragrant. Add the crushed tomatoes, chipotles in adobo, and chicken broth and stir to combine. Remove from heat, transfer to a blender, and puree until smooth.
Pour the sauce back into the dutch oven and add the bay leaf. Then add the chicken into the sauce so it’s completely submerged, and simmer until the sauce slightly reduces, and the chicken is completely cooked (when the chicken registers at 165 degrees Fahrenheit with an instant read thermometer.)
Once the chicken has fully cooked, transfer to a plate to shred; I like to do this with two forks, by using one fork to hold the chicken steady, and the other to pull the chicken into shreds. You could also cut the chicken into small strips and then shred with forks. Stir chicken back into sauce on a low heat so it’s well incorporated.
Spoon chicken into warmed tortillas (the absolute BEST way is to toast the tortillas directly over a low flame on your stovetop, and flip when slightly charred) and top with diced white onion, freshly chopped cilantro, and freshly squeezed lime juice. Enjoy!