Preheat oven to 350 degrees F.
Combine chicken, 1 cup each of cheddar, 1 cup of jack cheese, and 1 to 2 cups of enchilada sauce (2 cups for extra saucy, shown here)
Pour 1 cup of enchilada sauce in the bottom of a 9x13 casserole dish.
Lay a tortilla in the baking dish, allowing some sauce to spread onto the tortilla.
Spoon filling into the tortilla and roll it up, tucking it in place against the side of the dish.
Repeat filling and rolling the remaining tortillas, filling the baking dish.
Pour another 1 to 2 cups of sauce over the tortillas, adjusting the amount for your personal preference.
Sprinkle with remaining cup of cheddar and remaining cup of jack cheese.
Sprinkle with cotija cheese.
Cover with aluminum foil and bake for 20 minutes.
Remove foil and bake 10 to 15 minutes longer until cheese is melted and sauce is bubbly throughout the dish.
Garnish with chopped cilantro, jalapeno slices, and avocado if desired.
Serve while hot.