Step 1

Season chicken generously with salt and pepper. Heat oil in a medium saucepan over high heat until shimmering. Add chicken skin side down and cook, without moving, until well browned, 6 to 8 minutes. (Lower heat if pot is smoking excessively or chicken starts to burn.) Flip chicken and cook on second side for 2 minutes. Transfer to a large plate and immediately add tomatillos, tomatoes, and garlic to pot. Cook, flipping occasionally, until blistered and browned in spots, about 5 minutes.

Step 2

Add onion and cook, stirring, until softened, about 2 minutes. Add oregano and bay leaves and cook, stirring, until aromatic, about 30 seconds. Add vinegar and stock. Return chicken to pot, bring to a boil over high heat, then reduce to a bare simmer. Cover the pot and cook, turning chicken occasionally, until chicken registers 145°F when an instant-read thermometer is inserted into the center of the thickest part, 20 to 30 minutes. Transfer chicken to a bowl and set aside. Continue cooking the sauce at a hard simmer, stirring, until reduced to about half its original volume, about 5 minutes longer.

Step 3

Add chipotle chilies and adobo, remove and discard bay leaves, and blend the sauce using an immersion blender or by transferring to a countertop blender. Sauce should be relatively smooth, with a few small chunks. When chicken is cool enough to handle, discard the skin and bones and finely shred the meat. Return it to the sauce. Add fish sauce and stir to combine.

Step 4

Bring to a simmer and cook, stirring, until sauce thickens and coats chicken. It should be very moist but not soupy. Season to taste with salt and pepper (if necessary). Chicken tinga can be served in tacos; stuffed into enchiladas or burritos; on top of nachos, tostadas, and sopes; or on its own.