Mustardy pork mayo filling: Gently warm the shredded pork in a pan or in the microwave. It shouldn’t be hot – just slightly warmed through if it has been refrigerated. Stir together the mayonnaise, mustard(s), lemon juice and honey. Add a small pinch of salt, so the meat is well seasoned, then fold the dressing through the pork until evenly coated.
To serve: Slice the bagels and lightly toast them in a toaster or air fryer. Spread both cut sides with a little butter. Layer the bottom halves with lettuce, tomato slices and avocado. Spoon over the pork mayo mixture and finish with the pickled onions. Close with the bagel tops.