Grilled Beef and Marinated Fennel Sandwiches with Mustard Sauce

For an abundant beef sandwich, opt for a rib-eye steak due to the fact that it's marbled, and therefore rich in flavour. Choose a thick cut so that it's cooked until perfectly pink on the inside. Garnish with caramelized onions and a quick and easy Béarnaise sauce made with sour cream, mustard, tarragon and chopped pickles. It pairs wonderfully with the beef.