Grind the peppercorns with the red pepper flakes with a mortar and pestle. (Or grind roughly in a coffee grinder. Leave some texture.)
Put the pork cubes in a bowl and sprinkle with a bit of the salt and all of the crushed pepper, stirring it around to coat the pork. Then leave this to sit for 20 minutes or so.
Chop up the lettuce, slice the cucumber and herbs and divide between your plates. Drizzle a little vinegar and ponzu sauce over each and toss lightly.
Heat a heavy skillet over high heat and add the oil. When it shimmers, add the pork and sprinkle with a bit more salt. (She suggests flaky sea salt but I just used regular.) Stir fry the pork cubes until they are browned all over and cooked through.
Divide the pork between the two plates and sprinkle with the herbs and jalapeno.
Serve with lime wedges or just sprinkle some lime juice atop the meat.