Preheat oven to 400°F In a large saute pan over high heat, whisk the chicken broth, chipotle pepper and cumin until blended.
When boiling, add chicken breasts, lower heat to a simmer and cover. Poach for 10 minutes, turn breasts over and poach for an additional 5 minutes. Cut into the thickest part of one breast to check for doneness; if no pink remains, remove chicken to a plate to cool. If not done yet, return chicken to the heat, cover, and check every 2 minutes for doneness.
Dice chicken into ½ to 1 inch cubes and set aside. Return saute pan to high heat and begin reducing the chicken broth.
Meanwhile, in a medium saucepan over low heat, combine the condensed soup, milk, sour cream, cream cheese and chiles. Whisk until cream cheese is melted and well incorporated. Keep sauce over low heat.
When the chicken broth is thick enough to coat the back of a spoon, add olive oil and stir to combine. Then stir in the onions and garlic salt. Reduce heat to medium-high and stir occasionally until onions are quite soft, approximately 8-10 minutes. If the pan begins to dry, add water. When the onions are softened and surrounded by thick red liquid, turn off the heat, add the chicken and stir to combine.
Place tortillas on a plate. Microwave on high for 30-40 seconds, or until softened. Divide cooked chicken evenly between tortillas and top each with 2 tablespoons or so of cheese. Roll tortillas and place seam side down in a 9x13 dish that has been sprayed with Pam.
Pour sour cream sauce evenly over enchiladas. Top with remaining cheese and bake for 20 minutes at 400F until cheese is melted and sauce is bubbling around the edges of the baking dish. Serve with additional sour cream and green salsa, if desired.