Chicken Chilaquiles Verdes

Name: Chicken Chilaquiles Verdes
Ingredients: 1 large skinless, boneless chicken breast; 1 (16 ounce) jar salsa verde, divided; 1 cup chicken broth; 1 medium yellow onion, chopped; 1 teaspoon chili powder; 1 teaspoon ground cumin; 0.5 teaspoon cayenne pepper; salt and freshly ground black pepper to taste; 2 tablespoons olive oil; 8 (6 inch) soft corn tortillas; 0.5 cup sour cream; 1 tablespoon milk, or more as needed; 2 tablespoons crumbled cotija cheese, or to taste; 0.25 cup chopped fresh cilantro