Roast the chile peppers using your preferred method. Once they have blackened, peel them and remove the stems and seeds. Then place the cleaned peppers in a blender with the water, and garlic. Blend well, and then add the rest of the ingredients for the sauce. Blend again and set aside.
Heat the pan with some oil. Add the beef and cook until almost brown. Add the garlic, salt, and half the scallions. Once the beef has browned, drain, and add the sauce. Let simmer for about 10-15 minutes. Set Aside.
Warm all the tortillas using your preferred method. Add a little sauce to a 9x13 casserole dish, enough to barely cover. To make the first layer, place six tortillas and add about 3 cups of the beef and sauce mixture, making sure you add more meat than sauce. Sprinkle 1 cup of cheese on top. Repeat for the second layer. For the last layer, you should have more sauce than meat. Top with 1 1/2 cups of cheese and scallions.
Place in an oven until cheese browns (about 10 minutes in a 425 degree oven).