Gwen and Karen, Here is a tartar sauce that I use, I am not familiar with the restaurant that you speak of so I do not know if it is what you are looking for but this is a good one.
1 Tbsp. dry minced onion
2 Tbsp. water
2 3/4 Tbsp. dill pickle relish,drained
2 Tbsp. juice from dill pickle relish
1 tsp. French's prepared yellow mustard
1 cup mayonnaise
7 drops Tabasco sauce
Combine dry onion and water and set aside for about 5 minutes to let most of the water be absorbed. Drain any excess water after 5 minutes.
Combine with remaining ingredients. Refrigerate until serving time.