Rub chicken breasts with salt and pepper on both sides.
In a large pot, heat oil and sear the chicken until golden on both sides. Set aside.
In the same pot, sauté garlic with chili powder, cumin, and onion powder until fragrant.
Pour chicken stock into the pot, scraping the bottom for flavor. Return the seared chicken to the pot and simmer for 30 minutes.
Remove the chicken, shred, and return it to the pot.
Mix reserved stock with masa harina and slowly whisk it into the soup. Add enchilada sauce and simmer for another 30 minutes, stirring occasionally.
Turn off heat and stir in half of the cheeses. Serve with your desired toppings.
