Make the pork marinade: finely mince the Garlic and Shallots and combine with Light Soy Sauce, Dark Soy Sauce, Fish Sauce, Sugar, Five-Spice Powder and Ground Black Pepper. Rub the mixture over the Pork Shoulder and let marinate at least 1 hour, preferably overnight in the fridge.
Render the pork fat and crackle: cut the Pork Fatback into small pieces and cook slowly in a dry skillet until the fat renders and the pieces turn golden and crisp. Remove the cracklings and reserve the rendered fat for searing.
Sear and braise the pork: heat a splash of Neutral Oil and a little of the reserved fat in a heavy pan, sear the marinated Pork Shoulder on all sides until caramelized, then add just enough water to come a third of the way up the meat. Cover and simmer gently until very tender (45–90 minutes depending on size). Remove the pork and rest, keeping the braising liquid in the pan to reduce into a glaze if desired.
Make the clear pork broth: in a large pot, combine Pork Bones with cold Water, a halved Onion, smashed Ginger, Star Anise, a Cinnamon Stick and a piece of Rock Sugar. Bring to a boil, skim, then lower to a simmer and cook 1.5–3 hours. Strain and season to taste with fish sauce and a pinch of salt.
Prepare the noodles and vegetables: bring a pot of water to a rapid boil and cook the Cao Lầu Noodles until just tender; drain and rinse briefly under warm water to keep them springy. Quickly blanch the Bean Sprouts in boiling water for 10–20 seconds and drain. Tear or thinly slice the Romaine Lettuce.
Finish the pork: thinly slice the rested braised Pork Shoulder. If you reduced the braising liquid to a glaze, toss the slices briefly in the glaze over medium heat so they’re glossy and flavorful.
Chop the herbs and aromatics: roughly chop Mint, Vietnamese Basil, Cilantro and thinly slice the Spring Onions. Cut the Lime into wedges and slice the Bird's Eye Chilies thinly for heat.
Warm the sesame rice cracker and assemble: warm the Sesame Rice Cracker briefly over the flame or in a low oven so it cracks easily; break into pieces. In serving bowls place a bed of Cao Lầu Noodles, a handful of Romaine Lettuce and Bean Sprouts, then arrange the glazed Pork Shoulder slices on top.
Ladle a few spoonfuls of the hot broth over the bowl (you want it moistened but not soupy), scatter the crisp pork cracklings from the Pork Fatback, sprinkle the chopped Mint, Vietnamese Basil, Cilantro and Spring Onions, then crumble some Sesame Rice Cracker over everything.
Finish and serve: squeeze fresh Lime over the bowl and add sliced Bird's Eye Chilies to taste. Serve immediately so the cracker stays crunchy and the noodles keep their springy texture.
