1. In a small bowl, whisk the soy sauce, bourbon, brown sugar, garlic, and ½ teaspoon sesame oil until the sugar dissolves. Place the steak in a large resealable plastic bag and pour the marinade on top. Seal and massage the marinade into the meat. Let stand at room temperature while you heat the grill or refrigerate for up to 4 hours. 2. Heat an outdoor grill to medium-high or heat a cast-iron grill pan on the stovetop. 3. When the grill is ready, remove the steak from the bag and wipe off any excess marinade. Pour the marinade into a small saucepan. Grill the steak for 12 minutes, turning once halfway through, for medium-rare. Transfer to a cutting board and let rest for 5 minutes. 4. Meanwhile, bring the marinade to a boil and boil for 3 minutes. Reduce the heat to low and whisk in the gochujang and remaining ½ teaspoon sesame oil until well-combined. 5. Cut the steak across the grain into thin slices. Divide the rice and steak among the lettuce leaves. Drizzle with the sauce and top with the scallions.