In a large bowl combine ground beef, brown sugar, ginger, soy sauce, sesame oil, green onions, salt and pepper. Form into four hamburger patties.
Preheat a skillet to medium-high heat, add the butter and let it melt. Place the hamburger patties into the skillet and grill for about five minutes on side one, flip, and continue to cook for additional three minutes or until medium-well. Remove hamburger patties from skillet and place on a plate to rest before serving.
To serve, place a patty on the bottom of a burger bun. Top the patty with lettuce, cheese, ketchup, Sriracha, and pickled onions. Place top hamburger on top and serve.