Ago Dashi (あごだし, grilled flying fish stock)

Ago dashi begins with a fish that has already met the fire. Dried flying fish, roasted until tawny and fragrant, gives a stock sweeter and rounder than katsuo dashi, with a clean finish that suits New Year clear soup and a fine bowl of udon. It sounds like a special-occasion stock because it is. That doesn't make it difficult.

The one detail that decides it is restraint. Yaki-ago, grilled dried flying fish, needs time in cold water so its flavor opens before heat tightens it. Bring it up slowly with konbu, then stop before the kelp boils. Boil konbu and it turns the broth faintly bitter and slick; boil the fish hard and the stock grows cloudy and harsh. We are coaxing, not extracting by force. There is a difference, and the pot knows it.

Good ago dashi should be pale gold, clear, and quietly sweet, not smoky in a loud way. Use whole grilled ago if you can find it, break it open, remove the bitter innards, and let the water do the honest work. This is honmono made reachable: one good ingredient, good water, and enough patience to keep from bullying either.