Marinate the Pork: Place the pork shoulder in a large Ziploc bag and pour over enough Chinese BBQ sauce (char siu sauce) to fully coat the meat.
Cook the Pork: Preheat the oven to 375°F (190°C). Remove the pork from the marinade and place it on a baking sheet lined with parchment paper. Cook the pork for 40-50 minutes or until the internal temperature reaches about 190°F (88°C) for a tender, juicy roast. Once done, untie the pork and slice it into thin strips.
Prepare the Bao Buns: While the pork is cooking, steam the pre-made bao buns according to package instructions. Typically, it will take just a few minutes until they’re soft and warm.
Assemble the Gua Bao: Mix the sriracha mayo to your desired spice level and spread a generous amount on the inside of each steamed bun. Add a layer of sliced pork shoulder (about 2 slices per bun). Drizzle with hoisin sauce for extra flavor. Top with cucumber slices, chopped green onions, fresh cilantro, and a sprinkle of sesame seeds. For an extra spicy kick, add some shredded red pepper from the tin.
Serve and Enjoy! Serve immediately and enjoy your delicious homemade Quick Gua Bao!