Turn the oven on to 375°F. In a large blender, mix the salsa verde and cilantro (if using) until smooth.
In a medium saucepan, heat the oil over medium heat. Stirring periodically, heat the salsa verde for one minute after adding it. After turning off the heat, whisk in the Mexican crema. Add an additional ¼ to ½ cup of Mexican crema for an extra creamy sauce.
Combine the shredded chicken and ½ cup of the green cream sauce in a big bowl, stirring to cover everything. If needed, taste and add salt for seasoning.
If you want to reheat the tortillas in the microwave, cover them with a moist paper towel and cook for one minute, turning them over halfway through to ensure they are all warm and soft.
In case you want to cook the tortillas, preheat a small pan with two to three teaspoons of oil over medium-high heat. After it's heated, gently cook each tortilla for ten seconds, turning it halfway through, or until it becomes soft. To drain off extra oil, transfer the tortillas to a dish covered with paper towels.
Transfer a quarter of a cup of the green cream sauce into a 9 x 13 baking dish. To coat, evenly distribute it over the bottom.
Place 1 ½ cups of shredded cheese and the shredded chicken mixture into the tortillas to assemble the enchiladas. Transfer the enchiladas, seam-side down, onto the baking dish that has been prepared, and cover with the leftover green cream sauce. Add the remaining cheese shreds on top.
Bake the cheese for 15 to 20 minutes, or until it is bubbling and melted. Add some sliced onions as a garnish, then serve right away.