Heat the oil in a large, deep skillet or pan (preferably non-stick) over medium heat. Add the chicken to the skillet and cook for 3 minutes per side, just to get the chicken going and to brown on the outside a bit.
Remove the chicken from the skillet and set on a plate or pan. Keep warm by loosely covering with a piece of foil and/or placing the plate in the microwave or oven. It will stay warm away from drafts. Don’t worry that it’s not cooked all the way through; it will finish cooking in the enchilada sauce.
Do not wash the skillet, set it back over medium-low heat and add the butter. When the butter is melted and foamy add the flour. Cook the mixture for 1 minute, stirring frequently.
Next, add the tomato sauce, prepared seasoning mix, and chicken broth, stir well to combine.
Raise the heat to medium-high, when the sauce comes to a simmer return the chicken to the skillet. Lower the heat to medium-low, cover and cook 15-20 minutes until the chicken is cooked through.
Keep the sauce at a simmer, if it’s not simmering, raise the heat a bit, if it’s boiling too vigorously, lower the heat. Turn the chicken about halfway through the cooking time and stir the sauce occasionally.
Use an instant read thermometer to make sure the internal temperature of the chicken is at least 165°F at its thickest part.
Remove the chicken from the skillet and continue cooking the sauce, covered on medium-low to low heat for 10 minutes, stir occasionally.
Take the sauce off the heat and stir in the heavy cream. Taste the sauce and add salt if needed. As a reference we did not add any extra to ours.
While the sauce cooks shred the chicken when it’s cool enough to handle. Place it on a cutting board or pan and shred it using two forks.
Place the shredded chicken in a large bowl, add 1 cup of enchilada sauce, corn and black beans. Stir well to combine.
Preheat the oven to 350°F