How to cook the perfect beef stroganoff

This 70s favourite is overdue a revival. But do you stay authentically Russian with a flour-and-butter roux or add the sharper notes of sour cream and mustard?Named after, if perhaps not created for the 19th-century Russian celebrity count, stroganoff rolls off the tongue as richly as the dish itself. First mentioned in print in 1871, the notion of sautéed beef in a piquant, creamy sauce is much older – but the aristocratic Stroganov seems an appropriate patron saint for what is, af