Prepare Marinade: In a mixing bowl, whisk together soy sauce, fish sauce, brown sugar, lime juice, minced garlic, black pepper, and red pepper flakes.

Marinate Flank Steak: Place the flank steak into a resealable plastic bag, pour the marinade over and refrigerate for at least 1 hour.

Cook Jasmine Rice: Rinse the rice under cold water, combine with water and salt, then boil, reduce to low, cover, and simmer for 15-20 minutes.

Cook Beef: Heat oil in a skillet, sear the flank steak for about 4-5 minutes on each side until medium-rare, then rest for 5 minutes.

Slice Steak: Slice the steak against the grain into thin strips.

Assemble Dish: Serve jasmine rice as a base topped with sliced steak, garnish with cilantro and sesame seeds, and add cucumber slices.

Serve with Optional Dipping Sauce: Mix lime juice, fish sauce, and brown sugar in a bowl until sugar dissolves.