Make This Slow Cooker Chicken Tortilla Soup Packed With Flavor

Name: Make This Slow Cooker Chicken Tortilla Soup Packed With Flavor
Cuisine: American, Mexican, Latin American, TexMex
Ingredients: 2 boneless chicken breast halves; 1 medium onion (finely chopped); 1 clove garlic (crushed); 3 medium tomatoes (peeled, seeded, and chopped); 4 cups chicken broth; 1/4 teaspoon kosher salt (or to taste); 1/8 teaspoon freshly ground black pepper (or to taste); 1 mild green chile (seeded and chopped); 4 corn tortillas; 2 tablespoons vegetable oil; Optional: shredded Monterey Jack cheese (a tablespoon or two for each serving); Garnish: 2 tablespoons coarsely chopped fresh cilantro or Italian flat-leaf parsley