Prepare a marinade and mix with the sliced beef in a bowl. Let marinate for at least 30 minutes, preferably overnight.
Heat 2 tablespoons of vegetable oil in a pan over medium heat. Add the marinated beef and fry for 6 minutes until cooked through. Transfer to a bowl.
Add another 2 tablespoons of vegetable oil to the same pan over medium heat. Add the onions and ginger, sauté for 2-3 minutes until the onions are soft.
Return the cooked beef to the pan and stir for 1 minute until everything is evenly mixed.
Cook the brown rice according to package instructions. Divide into two bowls. Arrange cucumber and carrot pieces on the sides with the beef in the center. If desired, top with a fried egg and sprinkle with sesame seeds.