Chef John's Chicken Tinga Recipe

Ingredients

• 3 pounds skinless, boneless chicken thighs
• 4 cups chicken stock
• 1 cup water
• 1 large yellow onion, halved
• 3 peeled whole garlic cloves
• 2 teaspoons kosher salt, plus more to taste
• 0.5 teaspoon dried oregano
• 2 tablespoons olive oil
• 1 large onion, diced
• 1 (7 ounce) can chipotle peppers in adobo sauce
• 1 (28 ounce) can peeled plum tomatoes (preferably San Marzano)
• 3 tablespoons chopped fresh cilantro, or more to taste
• 2 tablespoons crumbled cotija cheese, or to taste