Preheat oven to 375 degrees.
In a small sauce pan, melt butter over medium heat. Add flour and mix to combine into a thick paste.
Gradually add chicken stock and stir until thickened, about 5 minutes.
Stir in sour cream and spices.
Pour into blender. Add avocado, cilantro, and lime juice.
Pulse mixture until combined. BE careful. Heat expands and may cause the lid to pop off your blender. Just to be safe, remove the top hole on your blender to let some air escape.
Drizzle olive oil in frying pan and add onions to cook over low heat until caramelized.
Prepare enchiladas by laying a tortilla flat, placing a line of avocado cream mixture down the middle, top with onions, chicken, and cheese.
Wrap tortilla around mixture and place tortilla in a greased baking dish, seam side down.
Continue until remaining ingredients are used.
Pour some avocado cream over enchiladas. Top with additional cheese if necessary.
Cover with foil and bake about 20 minutes, or until enchiladas are heated through.
Top with additional avocado cream, cilantro, and avocados if desired.