In a medium bowl, whisk together the fish sauce, brown sugar, soy sauce, sesame oil, garlic, ginger, and lemongrass. Add the pork and stir to thoroughly coat. Let sit at room temperature for 1 hour, or overnight in the refrigerator, bringing out 1 hour before cooking.

Heat the olive oil in a large wok over medium heat. Carefully swirl to coat the bottom half of the wok. Working in batches, cook the pork about 2 minutes per side until charred but not burnt. Remove and set aside. Scrape up and carefully remove any burnt flakes. Add the onions and cook until crisp tender ~ about 5 to 6 minutes. Add in the remaining marinade sauce and cook, stirring, until the onions absorb most of the sauce. Return the pork to the pan and heat through ~ about 1 minute.

Serve over rice garnished with scallions, cilantro, and a squirt of lime. Serve with fried bok choy, if desired.

Enjoy!