To make poached eggs, place the eggs in a saucepan. Pour boiling hot water into the saucepan to completely submerge the eggs. Cover with a lid for 18 minutes. After 18 minutes, remove eggs from hot water and place them in a bowl with ice water for 10 seconds. Crack the eggs into a bowl and set aside.
In a pan, combine the soy sauce, sake, mirin, brown sugar, Dashi powder, water, and ginger. Mix well, cover with lid and bring to a boil over high heat. Let boil for 1 minute.
Add the onions into the boiling soy sauce mix and cover with lid for about 5 minutes, or until the onions are completely tender.
Add the beef slices into the pan and cook for about 3 minutes while stirring occasionally, until the beef is fully cooked.
Place 1 1/2 cup of steamed white rice into a bowl and add half of the cooked beef, along with the onions and the sauce, on top of the rice bed. Place one poached egg on top and top everything off with some sesame seeds and green onions.