Mix dashi, mirin, soy sauce, sake, sugar, garlic, ginger, and pepper for broth.
Trim enoki base, rinse, pat dry, divide into 12 bundles.
Roll beef slices tightly around enoki bundles, leaving tops exposed.
Heat oil in pan, sauté onions for 1 minute.
Place rolls in pan, pour broth, cover, simmer 3–5 minutes.
Drizzle beaten egg (optional), cook 1–2 minutes more.
Garnish with scallions and sesame seeds, serve with rice.
