Step 1: Heat a large skillet or non-stick pan over medium-high heat. Add 1 tablespoon of olive oil. Once hot, add the ground beef to the skillet and break it up with a wooden spoon or spatula. Cook until browned and no pink remains.
Step 2: While the beef is browning, whisk together the soy sauce, brown sugar, minced garlic, grated ginger, rice vinegar, sesame oil, and optional gochujang in a small bowl until the sugar is dissolved.
Step 3: Once the ground beef is fully browned, drain off any excess fat from the skillet.
Step 4: Pour the prepared sauce over the cooked ground beef. Stir well to coat all the beef evenly and bring the mixture to a gentle simmer. Cook for 5-7 minutes, stirring occasionally, until the sauce thickens slightly and coats the beef.
Step 5: Stir in most of the chopped green onions and sesame seeds, reserving some for garnish. Cook for another minute.
Step 6: Taste and adjust seasonings as needed. Serve hot, garnished with remaining green onions and sesame seeds, over rice or your favorite grain.