Hollandaise sauce
The most common derivative is Sauce Béarnaise.  It can be made by replacing the acidifying agent (vinegar reduction or lemon juice) with a strained reduction of vinegar, shallots, fresh chervil, fresh tarragon and crushed peppercorns.  Alternatively, the flavourings may be added to a standard hollandaise. Béarnaise and its children are often used on steak or other "assertive" grilled meats and fish.