How do you make the seafood sauce at Japanese Steakhouse restaurants?

Question

How do you make the seafood sauce at Japanese Steakhouse restaurants?

Answer 1

You don't. They already have it made for you.

Answer 2

Based on the limited information given.  It's probably a combination of Dashi and soy sauce. Dashi is a Kombu (kelp) based broth. You can definitely buy it in your local Japanese market.  If you have a large enough Japanese population you might be able to buy it in the grocery store (that's where we get ours).