While oven is coming to temp, set your stovetop to high heat and heat vegetable oil in cast iron skillet. Mix Chinese 5 spice, brown sugar, salt & pepper into a dry rub and cover pork belly piece. Make sure to push the rub into the meat. Once the pork belly is covered, sear it in skillet for 4 minutes on each side to ensure that you have sealed in the juices. The pork belly should be nicely browned on each side but not burned. Pull the pork belly out of the skillet and let it rest.
Without emptying the “juices” and “bits and ends” from skillet, sauté onions and garlic for 2 minutes until browned on medium heat. Then add dark soy, star anise, water, rice vinegar, and brown sugar. Add pork belly to the braising liquid. The braising liquid should only rise to halfway up the pork belly. Once the oven has reached temp, place the skillet inside the oven and let it braise for approximately 3 and a half hours. Pork belly should be very moist and tender and you should be able to pull it apart at ease. Let pork belly rest after taking it out of the oven, then chop into smaller pieces.
Using Chinese mandolin, julienne daikon and carrot into thin strips. Mix daikon, carrot, rice vinegar, chili garlic, fish sauce and sugar. Let the mixture sit and rest.
Mix mayonnaise, sriracha, lime juice and rice vinegar together and place into a squeeze bottle.
Heat tortillas on griddle or stovetop, then add pork belly. Top with daikon/carrot mixture, sriracha mayo and cilantro.