You can use practically any cut of steak for this recipe. My favorite cut is the New York strip (aka shell, top loin or strip steak), but I chose a flank steak here to demonstrate another option. The flank steak can be put in a large Ziplock bag and marinated in the fridge for a longer period. Just remember to bring the steak back to room temperature before grilling.
1/2 Cup soy sauce
1/3 Cup dark rum
1/3 Cup packed brown sugar
1 Tablespoon Dijon mustard
2 Lb flank steak
In a small bowl combine soy sauce, rum, brown sugar and mustard, mix until the sugar has dissolved. Place the flank steak in a shallow baking dish and pour the marinade over the meat. Let the meat marinade at room temperature for 30 minutes.
When the grill is ready, remove the steak from the marinade making sure to shake off any excess fluid. Reserve the marinade. Grill the steak until distinctive sear marks appear, about 3 minutes. Next rotate the steak 90 degrees (to get a cross hatch of grill marks) and continue grilling for another 3 minutes. Flip the steak and grill the other side the same way until the outside is nicely seared and the steak is cooked to your liking. Cooking for 10 to 12 minutes should be medium rare. Let the stakes rest for 5 minutes before cutting.
Meanwhile, pour the marinade into a small saucepan and boil over a medium high heat until syrupy, about 3 minutes. Slice the steaks thinly across the grain, and serve drizzled with the sauce.