-
1
Partially freeze the beef for 30 minutes, then shave to 2–3 mm — the same thickness as shabu-shabu. The slices must be translucent at the edges. Set aside.
-
2
Place the water and kombu in a wide, shallow pan. Bring to a gentle simmer over medium heat, then add the soy sauce, mirin, sake, and sugar. Stir once to dissolve the sugar. The broth must read in balance — neither sharply salty nor overtly sweet — before anything else enters the pan. This is where the dish lives or dies: a broth tipped too sweet or too flat by skipping the kombu produces a one-dimensional result no amount of correction can fully remedy.
-
3
Add the sliced onion to the simmering broth. Cook until the onion is translucent and has softened into the liquid, carrying its sweetness into the broth. The onion should yield completely to light pressure.
-
4
Lay the shaved beef across the surface of the broth in a single layer. Simmer for exactly 90 seconds — the residual heat of the sweet broth continues to cook the beef after the pan leaves the heat. The beef is done when it has just lost its raw colour but retains a faint blush at the centre of each slice; grey, curled meat has been over-simmered.
-
5
Place hot steamed rice in each bowl. Ladle a measure of the broth over the rice first, allowing it to absorb into the grain. Arrange the beef and onion over the rice. Place a raw egg yolk on top of the beef — it is broken and mixed in by the diner at the table, creating a silky fat-rich coating over the beef. Set beni-shōga at the side of the bowl, not mixed in. Offer shichimi pepper separately.