1. Prepare hoisin sauce: Place all ingredients in a pint-sized mason jar, secure the lid, and shake until well combined. Store in fridge until ready to use.
2. Prepare the Char Siu: Cut the pork into long strips about 3 inches thick.
3. Combine 1/4 teaspoon of the hoisin per serving with the rest of the ingredients in a bowl to make the BBQ sauce. Reserve about 2 tablespoons of the sauce and pour the rest into a large zip top bag along with the pork. Make sure the pork is coated with the sauce, squeeze the air out of the bag, and seal it.
4. Marinate in the refrigerator overnight. Store the reserved sauce for later as well.
5. Preheat your oven to 475F with a rack placed on the highest position.
6. Line a sheet pan with parchment and place a metal rack on top to keep the pork off of the pan and allow it to roast more evenly.
7. Place the pork on the racks, leaving as much space as possible between pieces, and put the pan in the upper portion of the oven.
8. Pour the rest of the marinade from the bag into a bowl for basting.
9. After 25 minutes or so, flip the pork and baste with some of the marinating liquid.
10. If needed, add a half cup of water to the bottom of the sheet pan to prevent burning or smoking from the drippings.
11. After another 20-25 minutes, turn on the broiler to crisp the outside of the pork, but watch carefully to avoid burning the meat.
12. Remove from oven and use a basting brush to brush the roasted pork with the reserved BBQ sauce. Let the meat rest for ten minutes and enjoy!