Preheat oven to 350℉.
Melt 2 tablespoons of butter in a large skillet over medium heat. Add the sliced scallions and minced garlic. Saute for about two minutes or until the onions soften a bit and the garlic is fragrant.
Turn off the heat. Add in the diced green chiles, cream of mushroom soup, and 1 cup of sour cream. Stir until combined. Season with salt and pepper to taste.
Remove 1 cup of the mixture to a medium sized bowl. Add the milk and stir to combine. This will be the white enchilada sauce.
Pour about ½ cup of the enchilada sauce into the bottom of a 9X13 baking dish sprayed with cooking spray.
To the remaining mixture in the skillet, add the cooked chicken and 1 cup of the shredded cheddar. Stir to combine.
Spoon the chicken mixture evenly into each of the tortillas.
Roll enchiladas and place seam side down in prepared baking dish.
Continue to do this until the pan is full. Don't be afraid to really tuck them in tight. I can usually fit 10.
Spoon the enchilada sauce over the top using the back of your spoon to spread it evenly over the enchiladas.
Sprinkle the remaining cheese on top. Cover with foil and bake in the preheated oven for 20 minutes.
After the 20 minutes is up, uncover and place back into the oven until the cheese starts to brown and get bubbly. About another 5-10 minutes
Remove from the oven and let the enchiladas rest for about 10 minutes before serving