Heat olive oil in a large pot over medium heat. Add chicken breasts and cook for 6-8 minutes per side until fully cooked (165°F internal temp). Remove, shred with forks, and set aside.
In the same pot, add diced onion and sauté for 3-4 minutes until translucent. Add garlic and cook for 30 seconds until fragrant.
Pour in enchilada sauce, chicken broth, corn, black beans, diced tomatoes, cumin, chili powder, salt, and pepper. Stir well.
Bring to a boil, then reduce heat and simmer for 15 minutes. Add shredded chicken back to the pot.
Stir in heavy cream and cheddar cheese until melted and smooth. For a thicker texture, blend 1-2 cups of soup (optional).
Ladle into bowls and top with tortilla strips, avocado, cilantro, and sour cream.
