Nitsume or Thick, Sweet Eel Sauce for Sushi

Ingredients

1 cup dashi (cooking stock)
1/2 cup mirin (Japanese sweet cooking wine)
1/2 cup shoyu (soy sauce)
1/4 cup sugar

Directions

1. Put all ingredients into a saucepan, and heat to boiling over medium heat.
2. Simmer the sauce for about 3-4 hours to thicken. Reduce the volume to the point that it threads or webs when picked up 

 or if u can find this in asian market or on amazon~