In a large bowl, combine the ground beef, soy sauce, brown sugar, sesame oil, garlic, ginger, and black pepper. Mix until just combined, being careful not to overwork the meat.

Divide the mixture into four equal portions and shape them into patties.

Preheat a grill or skillet over medium-high heat.

Cook the patties for about 4-5 minutes on each side, or until they reach your desired doneness.

While the burgers are cooking, in a small bowl, mix together the mayonnaise, gochujang, and rice vinegar until smooth.

To assemble the burgers, spread a generous amount of the spicy mayo on the bottom half of each bun.

Place a cooked patty on top, followed by chopped kimchi, shredded lettuce, cucumber slices, and green onions.

Sprinkle with sesame seeds if desired. Top with the other half of the bun.

Serve immediately with your favorite sides.