Boeuf à la Ficelle

This is an old-fashioned French dish, but has much to recommend it today, requiring the best-quality produce to be cooked as simply and in as healthy a fashion as possible. Of course, what you serve with it might change all that. I have a jar of ‘hot horseradish mustard’, which I like to mix with unsalted butter or cream to serve with the beef, and Fay Maschler, in her excellent book, Eating In, recommends hors