The Best Chicken Tinga Tacos

Name: The Best Chicken Tinga Tacos
Ingredients: 1 tablespoon olive oil; 1 cup roughly chopped sweet onion; 2 cloves garlic, minced; 1–2 chipotle peppers in adobo sauce, chopped; 1 teaspoon dried oregano; 1⁄2 teaspoon ground cumin; 3⁄4 cup canned crushed fire-roasted tomatoes; 1⁄4 cup chicken stock; 1⁄2 teaspoon kosher salt; 3 cups shredded cooked chicken (rotisserie chicken works!); For Serving:; 10 (6-inch) corn tortillas; 2 ripe avocados, sliced; 1/4 cup chopped fresh cilantro; 1/2 cup diced red onion; crumbled cotija; 1 lime, cut into wedges