In a large ziplock bag, add your sliced beef, salt, pepper and cornstarch. Seal tight and shake until fully coated. Set aside.
In a large bowl, combine brown sugar, soy sauce, oyster sauce and warm water. Mix until the brown sugar has completely mixed into the sauce. Set aside.
Place a wok or skillet over medium high heat and add 2 tbs oil. Add in beef, making sure to shake off excess corn starch. Cook until beef is no longer pink, 3-4 min.
Once the beef is cooked and slightly crispy, remove it from the pan and add back in 1 tbs of oil. Let that heat up and drop in your onion, garlic, green onion stalks and chilies. Cook for 2 min and add the cooked beef back in.
Pour your sauce into the pan and allow to reduce until thick and shiny, 3-4 min.
Remove from heat and top with thinly sliced green onions. Serve with steamed rice.
