Preheat oven to 400 degrees F.
For the salsa: On a baking tray, roast tomatillos, onion, garlic and jalapenos for 12 to 15 minutes. Transfer the roasted vegetables and any juices on the bottom of the tray to a food processor. Add the cumin, salt, cilantro, and lime juice and pulse mixture until well combined but still chunky.
Enchiladas: Meanwhile heat a 2 count of olive oil in a medium saucepan over medium heat. Add the onion and cook until soft and caramelized - this should take 5 to 7 minutes. Add the garlic and cumin then cook for a further minute. Sprinkle on the flour and stir to ensure the flour doesn't burn then gradually add the chicken stock to make a veloute. Continue stirring over a low simmer until the flour cooks and the liquid thickens. Turn off the heat, add half of the roasted tomatillo chile salsa, some additional fresh chopped cilantro and fold in the shredded chicken meat. Season, to taste, with salt and pepper.
Change the temperature of the oven to 350 degrees F and begin assembling the dish. Take a large baking dish and smear the bottom with some of the reserved tomatillo salsa. Now take the flour tortillas and briefly flash them over the stove-top flame (or put them briefly under the broiler if using an electric stove). Using a shallow bowl, coat each tortilla lightly with the reserved salsa mix. Put a scoop of the shredded chicken-enchilada mix on top of the tortilla followed by a sprinkle of the shredded cheese. Fold the tortilla over the filling and roll like a cigar to enclose it. Using a spatula place the tortillas in the baking dish and continue to do the same with all the tortillas. Finally pour over some more of the salsa and top with the remaining shredded cheese. Bake uncovered for about 30 minutes until bubbly and cracked on top. Garnish, cilantro and tomato.