1 teaspoon kosher salt
1/2 teaspoon ground black pepper
1/4 cup plus 1 tablespoon soy sauce
2 tablespoons canola oil (plus more for the grill)
1/4 cup minced fresh ginger
1-1/2 tablespoon minced garlic
3 tablespoons rice vinegar
2 tablespoons Asian sesame oil
1-1/2 tablespoons light brown sugar
2 teaspoon cornstarch
1 tablespoon sesame seeds, toasted
1. Season the flank steak with 1 tsp. of the salt and pepper. Mix 1 Tbs. of the soy sauce, 1 Tbs. of the canola oil, 2 Tbs. of the ginger, and 1 Tbs. of the garlic in a large zip-top plastic bag. Add the steak and turn and massage it in the bag to cover it with the marinade. Refrigerate for at least 4 hours or overnight (my preference).
2. Heat 1 Tbs. of the canola oil and the remaining 2 Tbs. ginger and 1/2 Tbs. garlic in a small saucepan over medium heat until the ginger and garlic sizzle and just begin to brown around the edges (about 3 minutes). Add 1/3 cup water, the remaining 1/4 cup soy sauce, and the rice vinegar, sesame oil, and brown sugar. Bring to a boil over medium-high heat. In a small bowl, whisk the cornstarch with 2 tsp. of water and stir it into the soy mixture. Cook until it returns to a boil and thickens slightly, about 1 min. Remove from the heat and set aside.
3. Heat a gas grill to medium high.
4. Clean and oil the grill grates. Grill the steak,covered, until it has good grill marks, 5 to 6 min. Flip and reduce the heat to medium. Cook, covered, until the steak is done to your liking, 4 to 5 minutes for medium rare (cut into the steak to check). Transfer to a large cutting board, brush with about a third of the sesame sauce, and let rest for 5 minutes.
5. Slice the steak thinly and serve with a drizzle of the remaining sesame sauce, and a sprinkling of sesame seeds.