Make the Viet pickle: Peel and cut the daikon into sticks about 3 inches long and ¼-inch thick. Peel and cut the carrot into sticks a little skinnier than the daikon. Toss with salt and 2 teaspoons sugar. Massage for 3 minutes or set aside for 20 minutes. (Until daikon can be bent without breaking, they will shrink in volume). Rinse, drain, and transfer to a jar. Stir together remaining sugar with vinegar and 1 cup water until dissolved. Pour over vegetables to fully cover and let sit for 1 hour. (We make a lot and let it marinate in a glass jar in fridge for later use. Can sit for one month)
Prepare the char siu chicken: Pat chicken thighs dry, trim fat, and butterfly if necessary. In a bowl, stir together garlic, five-spice powder, honey, hoisin, soy sauce, ketchup, and sesame oil. Remove 3 tablespoons for glazing. Coat chicken in marinade and let sit for 30 minutes. (We let it marinate for like 3 days on accident and turned out good lol). Bring back to room temp before cooking.
Cook chicken on a grill pan over medium-high heat for 6 to 10 minutes, basting with reserved marinade during the last 2 minutes. Let rest for 5 to 10 minutes before serving.
Make the sandwich: cut open bread (leave a hinge) Moisten bread crust and crisp in the oven. Open bread and hollow out some inside, and spread butter one side and mayo / Maggie mix other side. Layer chicken, cucumber, cilantro, chiles and pickled veggies inside. Salt pepper, close and cut to serve.
Also YouTube
https://youtu.be/k4HA1ejw_hA?si=1NNO5bY0tYW5tO6S