Packaged unagi kabayaki found in Japanese markets or
canned Hamanako Broiled Eels
Make a sauce of:
1 tablespoon shoyu (soy sauce)
1 tablespoon sugar
3 tablespoons sake
Put the sauce ingredients into a shallow pan and heat on medium-low heat until boiling and sugar has dissolved.
Add unagi from the package, also adding the juice from the package/can to the pot.
Simmer gently until heated through and the sauce reduces a little and thickens a bit. You could also cook the unagi under the broiler and spoon the sauce on top when it's done.
Serve over rice, garnish with chopped chives or green onions.