A quest begun some 25-ish years ago and put before me by a friend ends here with the perfect American nacho, Memphis style. It's a little bit drunk, sometimes hungover, and stone cold sober good. —thirschfeld
Combine all the ingredients for the sauce in a medium sized sauce pan and stir to combine. Place the pan over medium heat and bring the sauce to a simmer. Reduce the heat to low and let it sit for half and hour. Remove the sauce from the heat until needed.
Heat the oven to 500° F. Line an 18 x 13-inch half sheet tray with foil. Spread the shaved romaine lettuce across the bottom of the pan. Top with half the mozzarella and sprinkle with half the red onion. I know you think this step is crazy, but the wilted romaine that soaks up any and all juices will be your favorite part of the nachos. Trust me.
Lay the bag of chips on its side and open it from the bottom. This keeps all the broken bits on the bottom, and the whole, good-looking chips stay on top. Place the bag onto the lettuce bottom side-down, and lift it slowly. Spread the chips out if needed.
Place the cream in a small saucepan and bring it to a boil over medium heat. Add the slices of cheese, a slice or two at a time, only adding more when the first slices have melted. Be careful with the heat -- the sauce can scorch. When all the slices have melted, turn the heat down to a simmer.
Dress the pork with a couple of tablespoons of sauce just to dampen it. Don't bathe the pork in the sauce. Spread the pork out across the top of the chips, then sprinkle with the remaining mozzarella.
Place the nachos into the oven and bake 10 minutes or until the chips on top begin to brown. Remove the tray from the oven.
Using a large spoon, drizzle the warm barbecue sauce across the chips to taste. It doesn't require as much sauce as you might think, plus the pork is already coated too, and you can always serve more sauce on the side.
Spoon the cheese sauce across the top, then top with the green onion and the remaining red onion. Serve.