Heat the cooking oil in a frying pan. Swirl to coat the entire bottom.
Spread the ground beef in the hot oil, leave to brown the underside for a minute of so, then stir to break up lumps. Cook, stirring, until lightly browned all over.
Add the chopped onion and garlic. Cook, stirring occasionally, until the onion pieces are softened and appear translucent.
Season the meat
In a small bowl, mix together the grated ginger, soy sauce, rice wine, sugar and Worcestershire sauce.
Pour the mixture over the browned ground beef and cook, stirring often, until the liquid has been soaked up by the meat.
Stir in the gochujang and cook until fully incorporated.
Add finishing touches
Off the heat, drizzle in the sesame seed oil and sprinkle in the chili flakes.
Toss until the coloring looks uniform.
Serve your Korean ground beef over rice. Garnish with sliced scallions, toasted sesame seeds and your choice of vegetables on the side.