Heat a large skillet over medium-high heat.
Add the ground beef to the skillet and cook, breaking it apart with a spatula, until browned and cooked through, about 6-8 minutes.
Drain excess fat from the skillet if necessary.
Add the minced garlic and minced ginger to the beef and cook for 1-2 minutes until fragrant.
In a small bowl, whisk together the soy sauce, brown sugar, sesame oil, crushed red pepper flakes, and black pepper.
Pour the sauce mixture over the cooked beef in the skillet and stir to combine.
Cook for an additional 3-4 minutes, allowing the sauce to thicken slightly and coat the beef.
Remove the skillet from heat.
Serve the Korean beef over cooked white rice.
Garnish with sliced green onions and toasted sesame seeds before serving.