For the pickled vegetables: Heat the vinegar, sugar and salt in a small pot until the sugar and salt are dissolved. Pour the hot vinegar mixture over the daikon, carrots and cucumbers. Let steep for at least an hour.
For the spicy mayonnaise: Mix the mayonnaise, Sriracha and sesame oil together. Adjust the heat by either adding more Sriracha or mayonnaise.
For the pork: Heat the canola oil in a straight-sided skillet over medium heat. Add the onions and cook until slightly softened, 4 to 6 minutes. Add the ginger and garlic and cook another 2 minutes. Add 1/2 cup of the pickling liquid from the pickled vegetables and cook until reduced by half, 1 to 2 minutes. Add the chicken stock, fish sauce, hoisin sauce and black pepper and stir to combine. Simmer until reduced slightly and thickened, 10 to 15 minutes. Add the ground pork, breaking up the meat with the back of a wooden spoon or spatula, and cook until the pork is cooked through, 6 to 8 minutes.
For the sandwich build: Preheat the oven to 350 degrees F. Heat the rolls for 5 minutes, to crisp the crust and soften the interior. Slice the rolls open, but keep them hinged. Schmear desired amount of spicy mayo on the bottom roll, place some pork on top of that, top with some pickled vegetables, fresh jalapenos, cilantro leaves, and finish with the chopped peanuts. Grab with two hands, eat whole and close your eyes while enjoying this first class ticket to Saigon.