In a small bowl, whisk together the soy sauce, brown sugar, sesame oil, rice vinegar, ginger, garlic, black pepper, and water to create the sauce. Set aside.
Heat the vegetable oil in a large skillet or wok over medium-high heat.
Add the ground beef to the skillet. Break the meat apart with a spoon and cook until it is fully browned. Drain off any excess grease.
Pour the prepared Bulgogi sauce over the cooked ground beef. Stir well to coat the meat completely.
Bring the mixture to a simmer. Reduce the heat to medium-low and cook for 3 to 5 minutes, stirring occasionally, until the sauce has thickened slightly and coats the beef.
To assemble the bowls, divide the cooked white rice among four bowls.
Spoon the ground beef Bulgogi mixture over the rice.
Garnish each bowl with sliced green onions and sesame seeds. Add any desired optional toppings.
Notes
For a gluten-free option, substitute tamari for the soy sauce.
If you prefer a lower-carb meal, serve the Bulgogi mixture over cauliflower rice instead of white rice.
You can prepare the Bulgogi sauce up to three days ahead of time and store it in the refrigerator.