In a large bowl, combine 2 tbsp. soy sauce, 2 tbsp. canola oil, the mirin, cumin, pepper and granulated garlic and onion. Add the steak; turn to coat. Let marinate 15 minutes.
Heat a griddle or grill pan over medium-high. Cook steak, turning once, 8 to 10 minutes for medium-rare. Transfer to a plate and let rest while you cook the vegetables.
In a large skillet, heat the remaining 1 tbsp. oil over medium-high to high. Add the bell peppers, edamame, onion, chiles and garlic. Cook, stirring often, until the vegetables are crisp-tender, about 6 minutes. Stir in the remaining 3 tbsp. soy sauce. Remove from the heat and stir in the shiso.
Thinly slice the steak against the grain. Drizzle with sesame oil and sprinkle with gomasio. Pile the sliced steak and vegetables in the lettuce leaves.