In a large skillet over medium-high heat, add the ground beef. Cook until browned, breaking it up with a spatula as it cooks. This should take about 5-7 minutes. Drain excess fat if necessary.
Once the beef is browned, add the diced onion to the skillet. Sauté for about 3-4 minutes until the onion becomes translucent. Next, stir in the pressed garlic and minced ginger, cooking for an additional minute until fragrant.
In a small bowl, combine the soy sauce, brown sugar, garlic powder, onion powder, and crushed red pepper flakes. Mix until the sugar is dissolved, then pour this mixture over the beef and onion in the skillet.
In another small bowl, whisk together the corn starch and water. Pour this mixture into the skillet, stirring well to combine. Cook for an additional 2-3 minutes, allowing the sauce to thicken.
Remove the skillet from heat and garnish with thinly sliced green onions. Serve the Korean Ground Beef Skillet over steamed rice, noodles, or in lettuce wraps for a complete meal!