Prepare and marinate the proteins: Slice pork belly into thin, bite-sized pieces. Detach shrimp heads and set aside. Peel and devein shrimp if preferred. In separate bowls, marinate pork and shrimp with salt, sugar, fish sauce, paprika, and turmeric. Set aside.
Build the broth: Heat 1 tablespoon oil in a large pot over medium-high heat. Add shrimp heads and cook for about 5 minutes, pressing them with a ladle to release their fat and flavor. Add sliced onion and coconut water. Bring to a boil, then reduce to a simmer and cook uncovered for 45 minutes.
Sauté pork and shrimpIn a separate pan, heat remaining oil. Add shallots and garlic and cook until fragrant, about 20–30 seconds. Add marinated pork and shrimp and cook for about 3 minutes until lightly seared. Transfer everything into the broth.
Season the broth: Season with fish sauce, salt, and sugar to taste. If needed, add a small pinch of MSG or chicken bouillon to enhance flavor. Simmer another 10–15 minutes.
Cook noodles: Cook noodles according to package instructions until tender but still chewy. Drain and set aside.
Assemble: Add noodles to a bowl. Ladle a small amount of broth over the noodles — just enough to coat. Top with pork, shrimp, and some broth solids. Add herbs, peanuts, lime, chili, and broken rice crackers. Toss before eating.