In a large skillet saute the onion and jalapeño in the oil, over medium high heat for 2 to 3 minutes, or until the onion is translucent. Add the shredded chicken and cook for 2 minutes.
Pour in 1/2 cup of chicken broth, 1/2 cup of heavy cream, 1/2 tsp of paprika, and 1/2 tsp of salt. Stir, and heat through. Remove and set aside.
In a separate large skillet melt the butter over medium heat. While whisking the butter in the pan, slowly sprinkle in the flour. Continue to whisk until it becomes clumpy, then slowly drizzle in the remaining 1 1/2 cups of chicken broth. Keep whisking until the mixture becomes smooth and starts to thicken slightly.
Pour in the remaining 1/2 cup of heavy cream and sour cream; stir.
Add 2 cups of Monterey Jack cheese, the remaining 1/2 tsp of paprika and stir until the cheese is melted. Peel and dice 2 avocados and add them to the cheese sauce; stir. Set aside.
Heat the corn tortillas in the microwave until they are soft and flexible. Place a small portion of the chicken mixture in the center, top with a couple slices of the remaining avocado, then roll up. Place seam side down in a 9x13 inch casserole dish. Repeat until tortillas and chicken mixture are used up.
Pour the cheese sauce over the enchiladas, and sprinkle with the remaining 1 1/2 cups of Monterey Jack cheese.
Bake for 20-25 minutes.
(optional: top with a little sour cream, and a side of salsa) Enjoy!