Allow 3 enchiladas per person. Use a Pyrex utility pan (13- 1 cm x 8- 0.75 inch) to cook them. Lightly grease the utility pan (for authenticity use lard). Preheat the oven to 400. Chop onions and grate cheese. Saute the onions lightly in 2 T. oil. Melt lard in a skillet; stir in the flour and make a light roux. Add ground chiles or chile powder, water and salt, and cook until thick. Of commercial chile powders, Gebhardt's from San Antonio is best, but not as good as ground chiles pasillas. Heat the remaining oil in a skillet. Using kitchen tongs, dip each tortilla in hot oil until well softened (about 15 seconds). Hold tortilla up and allow oil to drip back into the skillet. Using the tongs, dip tortillas in chili gravy. Place the tortilla in the Pyrex pan, put a good-sized pinch of cheese and onions in the middle, and roll the tortilla, placing the flap side down. Continue filling and rolling tortillas until the pan is full. Pour more chili gravy on top of the enchiladas, sprinkle the top generously with more grated cheese, and pop into preheated oven. Cook only until the cheese begins to bubble (about 10 minutes). Serve immediately.