01 - Rinse the rice under cold water until the water runs clear. Cook according to package instructions or using a rice cooker.
02 - Heat a large skillet over medium heat and combine dashi, soy sauce, mirin, sake, and sugar. Stir to dissolve sugar.
03 - Add the sliced onion to the skillet and simmer for 5 minutes until softened.
04 - Add the thinly sliced beef to the skillet, spreading the pieces apart. Simmer 3 to 5 minutes until just cooked through.
05 - Taste the sauce and adjust seasoning if desired.
06 - Divide cooked rice among four bowls. Top with beef and onions, spooning sauce over the rice.
07 - Garnish with sliced green onions, pickled ginger, and optionally a soft-poached or raw egg. Serve immediately.