Season the ground beef with garlic powder, salt, and pepper.
Heat a skillet over medium-high heat. Add the beef in a flat layer, sear undisturbed 2 to 3 minutes, then break apart. Cook until no longer pink, about 6 to 8 minutes. Remove.
Add the olive oil. Place the Brussels sprouts cut-side down in a single layer.
Cook undisturbed 4 to 5 minutes, until browned. Stir and cook 2 to 3 minutes more.
Add the garlic and cook 30 seconds until fragrant.
Whisk together the soy sauce, honey, rice vinegar, and chili flakes.
Return the beef to the skillet. Pour in the sauce and toss to coat.
Cook 1 to 2 minutes more, until heated through and glazed. Top with scallions and sesame seeds.