Use pork shoulder (pork neck) for this recipe. Make sure it is thinly sliced. You can find pre-sliced pork shoulder in Korean stores.
Mix chili paste, chili flakes, soy sauce, rice wine, sugar, garlic, ginger puree, sesame oil, sesame seeds, and black pepper in a small mixing bowl.
Add pork to gochujang sauce and mix well. You can make this step ahead of time and let it marinate in the fridge up to 24 hrs.
Heat oil in a deep skillet or wok over high heat. Add 2 teaspoon of sugar and swirl the pan around. Let the sugar turn brown and caramelized.
Quickly add the chopped Asian leek (or green onion) and stir-fry for 30 seconds to infuse the oil.
Add the gochujang sauced pork and onion. The meat should sizzle right away when you add it to the skillet.
Stir-fry pork and onion until they are fully cooked and tender. Serve immediately with rice and lettuce.
Serve hot with rice and lettuce wrap.