Crispy stir-fried pork: slice the pork into very thin slices and put the slices in a medium-sized bowl. Add cornstarch and 1/2 teaspoon of salt. Toss the meat until it is fully coated with cornstarch.
In a large pan over medium heat, add 3 tablespoons of oil. Once the oil is shimmering, add pieces of pork to the pan. Make sure you do not overcrowd the pan, or you will steam the meat. If you have more meat than will fit comfortably in the pan, cook the meat in batches. Later, when the sauce is almost finished the meat will have an opportunity to warm up again, so if you have to cook it in 2 or 3 batches that will be fine.
Cook each piece of pork for 3 minutes on the first side and an additional 2 to 3 minutes on the second side to ensure that it is a bit crunchy and cooked through. Remove each piece of pork to a plate while you cook the next batch.
Once the pork is fully cooked and moved to a plate to rest, add the onions and jalapenos to the pan and cook them for 3 to 4 minutes until the vegetables have softened.
Sweet and spicy sauce: while your onions and jalapenos are cooking, it's time to make the sauce. Add each sweet and spicy sauce ingredient to a medium bowl and whisk to combine.
Pour the sauce into the pan with the onions and jalapenos and cook until the sauce starts to thicken which should take about 5 minutes.
After the sauce has cooked for 4 or 5 minutes add the pork back to the sauce and stir to combine everything.
Sandwich assembly: slice your rolls and add half of the pork and sauce into each roll (there might be some leftover).
Top the pork and sauce with more fresh jalapeno slices, a sprinkling of sesame seeds, and a few sliced green onions to garnish.
Serve and enjoy.
Notes:
This is not a typical cut of pork. Normally when I find pork butt or shoulder it's a much larger piece, closer to 4 or 5 pounds. Your butcher could probably cut a pound off for you, but you can also just buy a pork butt to smoke or slow-cook and slice off a pound for this recipe.
If you'd prefer chicken instead of pork, just buy chicken breast and cut it into thin pieces so that it will cook quickly. After that, you can follow the rest of the instructions exactly as they are written.
If you prefer less heat, I suggest leaving out the jalapenos. The red pepper flakes do add a little spice, but not very much. Most of the heat in this recipe comes from the seeds in the jalapenos cooking in the sauce.