Prep the ground beef. Add the ground beef to a small mixing bowl and sprinkle the salt, white pepper, and kosher salt over the top. Use your hands to mix the meat well, so that the spices are evenly distributed. Let the meat sit for 15 minutes while you prepare the other ingredients.
Cut the green onions. Cut the white/light green parts of the green onion into 1 inch pieces. Thinly slice the dark green parts and keep them separate.
Make the stir fry sauce. In a small bowl, stir the brown sugar and warm water together until the sugar is dissolved. Whisk in the soy sauce, oyster sauce, ginger, and sesame oil. Sprinkle the cornstarch on top and whisk until there are no lumps. Set the sauce aside.
Brown the beef. Preheat a large wok or nonstick skillet over medium heat for a full 5 minutes. Drizzle the oil into the pan so that the surface is well coated. Use your fingers to break off small pieces of the meat into the pan. The goal is to have larger, chunky pieces rather than a finely ground mixture. Let the beef cook for 3-4 minutes undisturbed until brown on one side, then flip and cook for another 2 minutes. Use a slotted spoon to transfer the meat to a bowl and discard all but about 2 tablespoons of the fat left in the pan.
Saute the broccoli and onion. Add the broccoli to the pan and let it cook for 3-4 minutes, until it’s starting to brown. Add in the chopped onions, sliced garlic, and the white/light green parts of the green onion. Cook for another 2-3 minutes, stirring often, until the onion is starting to soften.
Add the sauce. Return the beef to the pan with any juices and pour in the sauce. Cook for another 2-3 minutes, until the sauce is thick and coats the beef and broccoli. Sprinkle in the rest of the green onions and some sesame seeds and serve over steamed rice.