Take the Flank steak to room temperature one hour before cooking. Rub the surface of the meat with olive oil, salt and pepper.
While the steak is warming, prepare the sauce; quickly bring the ingredients to a boil and mix well. Be careful not to let it stick to the bottom. Only little bit of sauce is needed, if any. Flank steak is such a great piece of meat that it is not worth spoiling it with too much sauce.
Flank steak on the grill
Grill over direct heat until the meat is turning the colour. Other side as well. Then move it indirect heat and cook for 5-10 minutes. This meat should not be over cooked.
On a pan
Turn on the oven and set it for 150C degrees. Place an ovenproof steak pan on the stove and turn up the heat. Quickly fry both sides of the steak and place the pan in the oven for 5-10 minutes depending how well done you want it.
Take the Flank Steak on to a cutting board, cover with foil and let rest for a while.
Slice the steak crosswise into narrow pieces. Take it on a serving platter and drizzle the sauce over the top.