Recipe for brown sauce from benihanas?

My family went to a Japanese restaurant called Benihanas. They had a great brown sauce for chicken and steak but wouldn't tell us exactly what it was. Does anyone know what is in it, or can I buy something similar at a grocery store, or even what its called?Recipe for brown sauce from benihanas?
Benihana's Ginger Dipping Sauce



1/4 cup chopped onion

1 small piece ginger root

(or 1/8 tsp ground ginger)

1/2 cup soy sauce

1/4 cup rice wine vinegar



Combine all ingredients in blender and process until smooth.



This recipe yields about 1 cup of sauce.Recipe for brown sauce from benihanas?
* 1 yellow onion

* 2 tablespoons peeled and grated fresh ginger

* 1/4 cup fresh lemon juice

* 1/2 cup white vinegar

* 1 cup soy sauce



Directions



chop onion and grate ginger on a cheese grater or micro plane other wise it's kinda fiberous.place all ingredients in a food processor and pulse until well blended.