Sauté onions in butter in a medium saucepan until onions are soft and translucent.Mix in the flour to form a paste.Pour in half of the milk and whisk continually until well-combined with a wire whisk.
Add the rest of the milk and the bouillon and continue whisking until mixture thickens and begins to bubble.
Remove from heat. Season with salt and pepper.
Preheat oven to 350 degrees and grease TWO 9 x 13 pans.
In a large mixing bowl, stir together sour cream, yogurt, Cream of Chicken Soup, and chilis for the sauce.
Spoon about 3 Tablespoons of sauce down the center of a tortilla. Sprinkle with about 1 1/2 Tablespoons each of chicken and beans and 1 Tablespoon cheese. Reserve 1/2 Cup cheese for topping at the end.
Roll filled tortillas and place in greased pan. Repeat this process about 24 times. ;)
Spoon remaining cream mixture over the rolled enchiladas and top with remaining cheese.
Cover pan with foil and bake for 25 to 30 minutes.
Remove foil and bake for another 5 minutes. Top with green onions before serving.
This recipe makes two pans, so freeze one and save it for a busy day later. However, we usually eat a pan and a half and have the rest for lunch the next day.