Heat a large skillet over medium-high heat for about 2 minutes. Add the lean ground beef, along with minced ginger and garlic, cooking for 5-7 minutes. Use a wooden spoon to break the beef apart as it browns. Once fully browned and no longer pink, drain the excess fat.

In a bowl, whisk together the low sodium soy sauce, brown sugar, and hoisin sauce until thoroughly combined. Pour this mixture over the browned beef in the skillet. Stir to coat the beef evenly and let it simmer for 2-3 minutes, allowing flavors to meld.

In a small bowl, mix the cornstarch with a couple of tablespoons of water until smooth. Gradually add this mixture to the skillet, stirring continuously to avoid clumping. Cook for an additional 2 minutes or until the sauce has thickened.

Stir in the red pepper flakes and freshly ground black pepper. Mix in the chopped green onions, saving a few for garnish. Combine well and simmer for an extra minute to let spices bloom.

Spoon the Mongolian Ground Beef over steamed rice or cooked noodles for a hearty meal. Garnish with reserved green onions or sesame seeds.