Get your mise en place. Mince garlic, grate ginger, slice green onions. Whisk soy sauce, brown sugar, sesame oil, garlic, ginger, black pepper, and red pepper flakes in a bowl until sugar dissolves.
Heat a large skillet over medium-high. Add neutral oil. Add ground beef once oil shimmers. Let sear for 1 minute, then break up and cook until no pink remains (4-5 min). Do not drain.
Pour the pre-mixed sauce over the cooked beef. It will sizzle. Stir to coat everything.
Reduce heat to medium. Let simmer, stirring occasionally, until sauce reduces and becomes thick and glossy (3-5 min). It’s done when the sauce leaves a slow trail behind a spatula.
Turn off heat. Stir in most of the sliced green onions, saving some for garnish.
Serve immediately over hot rice. Garnish with reserved green onions and sesame seeds.