Chicken Tinga

Name: Chicken Tinga
Ingredients: 8 ripe Roma tomatoes (about 2 pounds), rinsed; 2-3 tomatillos (about 1/4 pound), husks removed, rinsed; 3 tablespoons vegetable oil; 1 cup chopped white onion; 2 garlic cloves, minced or pressed; 1/2 teaspoon dried oregano; 1/4 teaspoon dried marjoram; 1/4 teaspoon dried thyme; 1 1/2 teaspoons kosher or coarse sea salt, more or less to taste; 2 tablespoons sauce from chipotle chiles in adobo; 1 whole chipotle chile in adobo, chopped (optional); 5 cups cooked shredded chicken, or shredded rotisserie chicken; 1 1/2 cups chicken broth