Step 1

In small, heavy-bottomed pot, arrange chicken breasts in a single layer. Add quartered onions, smashed garlic cloves, bay leaf, salt, peppercorns, and enough water to cover.

Step 2

Bring to a boil, skimming scum that floats on top. Lower heat, cover, and cook in a barely a simmer for about 10 to 15 minutes or until thermometer inserted in the thickest part of chicken reads 165 F.

Step 3

With a slotted spoon, remove chicken from pot and allow to cool to touch. Coarsely shred chicken and keep warm.

Step 4

Strain liquid using a fine mesh sieve. Discard bay leaf and peppercorns. Reserve the softened onions and garlic and 1 cup of the broth.

Step 5

In a blender, combine chipotle peppers including sauce, tomatoes, the softened onion quarters, garlic, and 1 cup reserved broth.

Step 6

In a wide pan over medium heat, heat oil. Add onions and cook until softened.

Step 7

Add pureed chipotle tomato sauce, vinegar, cumin, and oregano. Bring to a simmer for about 2 to 3 minutes.

Step 8

Add shredded chicken and continue to cook for about 7 to 10 minutes or until heated and sauce is thickened.

Step 9

Season with salt, if needed. Serve hot.