Heat a large skillet over medium heat. Add 1 pound ground beef and 3 minced garlic cloves; break the beef into crumbles with a spatula and cook, stirring occasionally, until no longer pink (about 6–8 minutes).

Drain excess grease from the skillet and return the beef to the skillet.

In a small bowl, whisk together 1/4 cup packed brown sugar, 1/4 cup reduced-sodium soy sauce, 2 teaspoons sesame oil, 1/4 teaspoon ground ginger, 1/4 teaspoon crushed red pepper flakes, and 1/4 teaspoon pepper.

Pour the sauce over the cooked beef, reduce the heat to medium-low, and simmer for 1–2 minutes, stirring, until the sauce thickens slightly and the beef is evenly coated.

Serve the beef over 2 cups hot cooked white or brown rice and garnish with sliced green onions and sesame seeds.