Authentic Mongolian Beef Recipe

Ingredients

• 1 lb flank steak, sliced thinly against the grain
• 1/4 cup soy sauce
• 1/4 cup brown sugar
• 2 tablespoons vegetable oil
• 1 tablespoon minced garlic
• 1 tablespoon minced ginger
• 1/2 cup green onions, chopped
• 1 tablespoon cornstarch
• 1/4 cup water
• 1/2 teaspoon black pepper
• 1/4 teaspoon red pepper flakes (optional)