Pat dry both sides of the steak.  Liberally season the steak with the Serious Foodie Seattle Espresso Rub.  Wrap the seasoned flank steak tightly with plastic wrap, and refrigerate for at least 2 hours, or overnight. Sthe sauce over medium heat until it is reduced by one half. Add the mustard, rosemary, . Cook on low heat until the sauce is thick.

Remove the steak from the refrigerator at least 30 minutes before cooking; pre-heat a gas or charcoal grill.

To make the sauce: add the olive oil to a sauce pan, and heat over medium. Add the minced garlic, and saute until fragrant, about 60 to 90 seconds. Immediately add the wine and soy sauce, and reduce by 1/2 (about 5 minutes). Stir in the Dijon mustard, rosemary, brown sugar, and optional cayenne pepper. Simmer until desired thickness is achieved.

Place the steak on the grill, and cook to desired doneness - about 6 minutes per side for rare. It's best not to over-cook flank steak.

Transfer the steak to a plate, and let stand for 5 minutes before carving. Cut the steak across the grain, and serve with the sauce and the optional arugula fennel salad - see https://serious-foodie.devsquad.tech/versatile-vinaigrettes/