For the pork: Bash together the garlic, ginger, peppercorns, cilantro leaves and stalks and spring onions in a mortar and pestle until you have a smooth paste. Add the fish sauce and honey and mix through. Place the sliced pork in a bowl and add three-quarters of the paste, reserving the rest. Massage the paste into the pork, then cover with plastic wrap and refrigerate for at least 2 hours, preferably overnight.
For the pickled vegetables: Dissolve the sugar and salt in the rice vinegar. Fold in the carrot and cucumber ribbons and the sliced red chiles. Set aside at room temperature for at least 20 minutes.
For the cilantro-chile mayonnaise: In a blender or mini-chopper, blitz the mayonnaise with the green chile and cilantro. Transfer to a bowl and mix in the lime juice. Chill until needed.
Once the pork has marinated, thread the slices onto skewers and set aside on a plate.
Cook the pork over high heat on a grill or in a lightly-oiled cast-iron grill pan until cooked through and sizzling, 2 minutes per side. Baste with the reserved marinade to create a sticky coating.
To assemble the sandwiches: Split open the rolls; slather on one side with the cilantro-chile mayonnaise and sprinkle the other with a few drops of Maggi sauce, if liked. Add the shredded lettuce, followed by the drained pickled vegetables. Top with a warm pork skewer and scatter over slices of red chile, if using, and spring onions. Eat soon, while the pork is still warm and the lettuce and pickled carrot are still nice and cold.