Marinade¼ cup white balsamic vinegar¾ cup olive oil1½ teaspoons minced garlic1½ teaspoons Dijon mustard1 teaspoon fresh thyme leaves, chopped1 teaspoon cracked black pepper1½ teaspoons minced shallotsMeat1 skirt steak (about 2½ pounds)1 loaf French bread, lightly grilledMixed greensGrilled red onions optionalCheese slices optionalTomato slices optionalIn a glass measuring cup, combine all the marinade ingredients. Place the skirt steak in a glass baking dish or plastic sealable bag. Pour the marinade over. Cover dish or seal bag. Marinate no more than 3 hours.Preheat the grill to medium-high heat. Oil the grates.Remove the skirt steak from the marinade and wipe off the marinade.Grill the steak about 3 to 4 minutes per side or until medium-rare or no more than medium.Brush the inside of the bread with some olive oil and grill until just lightly browned.If grilling the red onions, put them on the grill before the steak and grill about 5 minutes on each side.Place some mixed greens on the bottom of the bread and place the whole grilled skirt steak on top. Scatter some grilled onions, cheese and tomato slices on it.Cut the loaf into individual sandwiches and serve.Adapted from a recipe by Randy Emert, executive chef.