Cook's Note: There is enough marinade for up to 1 1/2 pounds of pork. Buy a whole pork tenderloin (can't really buy any less) and cut off the 9 ounces needed for this recipe. Marinate and roast both pieces and use the extra char sui to make delicious sandwiches, fried rice or roast pork salad!
For the marinade: In a large bowl, combine the soy sauce, ginger, honey, bean sauce, rice wine, garlic and sprinkle with salt and pepper. Add the pork, cover with plastic wrap and leave in the fridge to marinate for as long as possible, preferably overnight.
When ready to cook, preheat the oven to 350 degrees F.
Remove the pork from the marinade and reserve the marinade. Place the pork in a roasting pan and roast until the internal temperature reaches 145 degrees F, about 40 minutes.
While the pork is roasting, bring the reserved marinade to a boil in a small saucepan. Once the marinade has boiled you can take it off of the heat. Baste the pork halfway through cooking with 2 tablespoons marinade. Cool the remaining marinade to room temperature.
When the pork is done, remove from the oven and let rest for 15 minutes, then cut the pork into 1/4-inch cubes. Toss the cubed pork in enough of the reserved, cooled marinade to coat. The pork mixture should be at room temperature before filling the pastry.
For the puffs: Preheat the oven to 400 degrees F. Line a roasting tray with parchment paper.
Cut each sheet of puff pastry into six 3-inch squares, for a total of 12. Brush the edges of each square with the beaten egg and then place a heaping teaspoon of the pork filling in the center. Fold the square in half to create a triangular pastry. Tuck the triangle ends under to round off the triangular shape.
Place on the prepared roasting tray and brush egg wash over the top. Sprinkle sesame seeds over the top of the pastries and cook in the oven until the pastry is golden, 18 to 20 minutes. Serve immediately.