Real Chiles Rellenos

Name: Real Chiles Rellenos
Ingredients: 4 large poblano peppers; 0.25 cup all-purpose flour for dredging; 0.5 cup shredded mozzarella cheese; 0.5 cup shredded Monterey Jack cheese; 0.5 cup shredded Cheddar cheese; 1 (14.5 ounce) can Mexican-style stewed tomatoes; 1 tablespoon vegetable oil; 0.5 onion, chopped; 1 clove garlic, minced; 1.5 cups chicken broth; 2 tablespoons distilled white vinegar; 1 teaspoon dried Mexican oregano, crushed; 0.5 teaspoon ground cumin; 0.5 teaspoon black pepper; 0.5 teaspoon hot pepper sauce (such as Cholula®); 0.125 teaspoon ground cinnamon; 1/3 cup all-purpose flour; 0.5 teaspoon salt; 5 egg whites at room temperature; 1 egg yolk, beaten; 1 cup oil for frying, or as needed; sour cream for garnish