slow-cooked enchilada soup

Ingredients

• 2 tablespoons vegetable or canola oil
• 1 - onion, diced
• 1 - green bell pepper, diced
• 3 teaspoons minced garlic
• - salt and pepper to taste
• 1 - 14.5 oz can diced tomatoes w/ chiles
• 4 cups chicken broth
• 1-1/4 pound boneless, skinless chicken breasts cut into 1" pieces
• 2 cups frozen corn
• 1 can black beans, drained, rinsed
• 1 tablespoon chili powder
• 1 teaspoon dried cumin
• 1/2 teaspoon dried oregano
• 1-1/2 cup shredded mexican-style cheese
• 1 cup sour cream
• - baked tortilla chips for garnish
• 1 - sliced avocado for garnish