In a mixing bowl, whisk together soy sauce, brown sugar, minced garlic, grated ginger, and sesame oil until well combined. Add the ground beef or bulgogi beef, ensuring each piece is coated in the marinade. Cover the bowl with plastic wrap and let it marinate in the refrigerator for at least 1 hour, or up to overnight for deeper flavor penetration.

After marinating, remove the beef from the refrigerator and divide it into four equal portions. Gently shape each portion into patties about ¾-inch thick, being careful not to overwork the meat. Create a small indentation in the center of each patty to promote even cooking.

Preheat the grill to medium-high heat, reaching about 375°F (190°C). Lightly oil the grill grates to prevent sticking.

Once the grill is hot, place the patties on the grates, ensuring enough space between each for even cooking. Grill for about 4-5 minutes on the first side, then flip and grill for another 4-5 minutes or until desired doneness is reached.

While the patties finish cooking, place the burger buns cut-side down on the grill and toast for about 1-2 minutes until lightly browned and crispy.

Remove the patties and toasted buns from the grill. On each bottom bun, layer a grilled patty followed by a generous scoop of kimchi and any additional toppings. Place the top bun to complete your Bulgogi Kimchi Burger.

Serve the assembled Bulgogi Kimchi Burgers immediately while still hot.