Tartare sauce (also known as tartar sauce) is a thick white sauce made from mayonnaise and finely chopped vegetables (usually including pickled gherkins[?], capers[?] and pickled onions[?]) which is frequently used to season fish and chips and other fried fish dishes.
... now in a form in which we can conveniently complete the square[?]. To "complete the square" is to add a constant (i.e., in this case, a quantity that does not depend on x) ...