For the pork belly filling, cut the pork belly into bite-sized slices and place them in a large bowl. Add the soy sauce, vinegar, chili powder, cane sugar, ground coriander, five-spice powder, minced ginger, and garlic, and mix everything together until the pork belly is coated in the marinade. Cover the bowl with plastic wrap and refrigerate overnight.
The following day, combine the flour, yeast, salt, lukewarm water, and vegetable oil in a large bowl and knead the ingredients by hand until a smooth dough forms. Cover the dough and let it rest for 5–10 minutes. While the dough is resting, heat a pan with some vegetable oil, remove the marinated pork belly from the refrigerator, and sear the meat until it's crispy and golden brown on the outside.
Preheat the oven to 400°F. Dust flour over a clean work surface, roll the dough out into a log, and cut it into 6 equal pieces.
Roll out the pieces of dough into small circles, place some seared pork belly and fresh cilantro in the center of each one, and sprinkle sesame seeds on top.
Fold the edges of each piece of dough up and roll everything into a ball, making sure to completely seal in the pork belly filling. Place the stuffed dough balls, smooth side facing up, on a baking tray lined with parchment paper.
Lightly press an apple slicer into the top of each stuffed dough ball to create the classic rosetta roll pattern. Brush the egg wash evenly over the surface of the rosetta rolls and sprinkle sesame seeds on top of the rolls. Transfer the baking tray to the oven and bake the rosetta rolls at 400°F for 20 minutes.
