Cook the rice

• Rinse the rice until the water runs clear.
• Cook the rice in a saucepan with water until tender, then keep warm.

Make the sauce

• Combine the dashi, soy sauce, mirin, sake and sugar in a bowl.
• Stir in the grated ginger until the sugar dissolves.

Simmer the onion

• Pour the sauce into a frying pan and bring to a simmer.
• Add the sliced onion and cook until softened and translucent.

Cook the beef

• Add the sliced beef to the pan, spreading it out in a single layer.
• Simmer until the beef is just cooked through and the sauce has reduced slightly.

Assemble the bowls

• Divide the warm rice between bowls.
• Spoon the beef and onion with the sauce over the rice.
• Scatter the sliced spring onion on top and serve.