Heat a tablespoon of oil in a large skillet over medium-high heat. Add the lean ground beef, breaking it apart, and sauté for 6-7 minutes until cooked through.

Stir in the diced onion, minced garlic, and grated ginger. Cook for 2 minutes until the onions are soft and translucent.

Lower the heat and pour in the soy sauce, brown sugar, gochujang, and sesame oil. Mix well and let it simmer for 5 minutes until the sauce thickens.

Butter the inner sides of the buns and toast them in a skillet over medium heat for 2-3 minutes until golden brown.

Assemble the Korean Beef Sloppy Joes by spooning the beef mixture onto the toasted buns and adding optional toppings.