Step 1

Season the chicken all over with salt and pepper. Place in a single layer in a 4-quart or larger slow cooker.

Step 2

Heat the oil in a medium skillet over medium heat until shimmering. Add the onion and cook, stirring occasionally, until soft, about 5 minutes. Add the garlic, cumin, oregano, bay leaf, and the 1 teaspoon of salt, and stir to combine. Stir in the tomato purée, chipotle peppers, and adobo sauce and bring to a boil. Reduce the heat to low and simmer for 5 minutes.

Step 3

Pour the sauce and onions over the chicken. Cover and cook until the chicken is cooked through and tender, 2 to 3 hours on the LOW setting or 1 to 2 hours on the HIGH setting.

Step 4

Turn off the slow cooker and transfer chicken to a clean cutting board. Remove and discard the bay leaf. Shred the chicken into bite-sized pieces with two forks. Return the chicken to the slow cooker and stir to coat with the sauce before serving in tortillas with toppings if desired.