Preheat oven to 400 degrees F. On a rimmed baking sheet, roast the tomatillos, onion, garlic and jalapeños for 15-20 minutes, until the tomatillos are bubbling and juicy. Transfer the roasted vegetables and any juices on the bottom of the tray to a food processor. Add the cumin, salt, and cilantro and pulse mixture until well combined but still chunky.
In a large bowl combine and shredded chicken with 1/3 of the fresh salsa verde, sour cream, and 2 cups of the cheese. Mix well, then salt and pepper to taste.
Change the temperature of the oven to 350 degrees F and begin assembling the dish. Take a large 9x13-inch baking dish and smear the bottom with some of the reserved salsa verde. Put a scoop of the shredded chicken mixture on top of each tortilla. Fold the tortillas over the filling and roll like cigars to close. Place the tortillas in the baking dish; you may have to squeeze them in.
Pour the rest of the salsa verde over the enchiladas and top with the remaining shredded cheese. Bake uncovered for 20-30 minutes until bubbly. Garnish with cilantro, avocado and tomato. Top with a scoop of sour cream!
Video
Notes
You can make the salsa verde several days in advance of preparing the chicken enchiladas, and keep them in an airtight container in the fridge.