Boil water and pour over soy steaks in a bowl. Let soak for 15 minutes.
While steaks soak, prepare the marinade: mix Provence herbs, salt, pepper, chilli flakes, hot mustard (4 teaspoons), oil (8 tablespoons), and soy sauce (8 tablespoons) in a bowl.
Squeeze the soaked steaks well to remove all water. Coat both sides with the marinade and refrigerate for at least 2 hours (longer marinating develops more flavor).
Prepare the salad: cut the romaine lettuce hearts, bell pepper, cucumber, and shallot into small pieces and toss together.
Heat a skillet over medium-high heat. Add the marinated steaks and cook for 4-5 minutes, turning several times, until golden brown.
Arrange the cooked steaks on plates with the salad and serve.