Step 1: Place the sliced onion on the bottom of the slow cooker, salt the pork shoulder well then place on top of the onions. Mix together all ingredients for the char siu sauce and cover the pork shoulder with the suace. Cover and set slow cooker on low, cook overnight.
Step 2: Remove the pork from the slow cooker, place on a pan and shred pork from bone. Let cool then cover and place in fridge until ready to be used.
Step 3: In a large saucepan mix together the hoison, ketchup, soy sauce, apple sauce, garlic, oil, pepper flakes and zest. Bring to a simmer over medium-low heat, cook for about 12 minutes.
In a small bowl mix together the agave, cornstarch and water then add to the saucepan. Bring back up to a simmer, cook until it thickens, about 2 minutes.
Add pork, toss to coat and reheat the pork. Remove from heat.
Step 4: Mix together the carrots, cabbages, and sesame seeds in a large bowl. In a smaller bowl mis together the rest of the slaw ingredients, whisking in the oil.
Step 5: Heat tortillas either in a pan or 10 at a time in the microwave, covered with a wet paper towel.
Step 6: To plate take a tortilla, place a heaping tablespoon of pulled pork on the tortilla, top with a large pinch of slaw, drizzle with dressing & fold tortilla to close, held by a cilantro leave w/ toothpick through it.