In a small bowl, whisk together soy sauce, brown sugar, sesame oil, minced garlic, grated ginger, and red pepper flakes. Stir until the brown sugar completely dissolves to prevent grittiness and ensure even caramelization.

Heat a large skillet over medium-high heat. Add the ground beef and break it apart with a wooden spoon. Cook for 5-6 minutes, stirring occasionally, until the beef is fully browned and no pink remains. Let some pieces develop a golden crust for added flavor.

Drain any excess fat from the skillet, leaving just enough to keep the beef moist. Pour the prepared sauce mixture over the browned beef.

Reduce heat to medium and let the mixture simmer for 3-4 minutes, stirring frequently. Watch as the sauce reduces and coats each piece of beef with a glossy glaze. If it reduces too quickly, add a tablespoon of water.

Remove from heat and immediately stir in the sliced green onions. The residual heat will soften them slightly while maintaining their fresh bite and vibrant color.

Divide warm rice among serving bowls and top generously with the glazed Korean beef. Sprinkle with sesame seeds and additional green onions for garnish.