It sounds pretty fancy, but this butter sauce loaded with shallots and tarragon is a no-brainer. One of our favourite ways to dress up grilled steak, it also tastes terrific over chicken or lamb.
Prepare sauce up to the point of adding butter. Let cool, then cover and refrigerate overnight. Just before serving, warm sauce, then whisk in butter. Or microwave, uncovered, on medium-low, stirring every 15 seconds, just until warm, about 1 minute, then whisk in butter.