Prepare the Vinaigrette: In a small mixing bowl, whisk all ingredients together until thoroughly combined. For best results, allow flavors to marry overnight, stored in the refrigerator.
Meanwhile, Marinate the Steak: In a nonreactive dish or large Ziploc bag, combine all of the marinade ingredients. Mix well. Add the steak and turn to coat. Cover dish or seal bag and allow to marinate for 30 minutes at room temperature, or up to 24 hours in the refrigerator, turning to coat periodically. If you are refrigerating steak, remove it from refrigerator 30 minutes before cooking to bring it to room temperature.
For the Salad: In a large bowl, mix all of the salad ingredients except the steak and the peanuts. Toss with half of the vinaigrette until salad is well coated. Divide salad between serving plates.
Cook the Steak: Heat grill, cast iron skillet or grill pan to medium high and lightly oil grates. Remove steak from marinade, shaking off excess and add it to grill. Season with salt and pepper. Cook for 2-4 minutes per side for medium rare (depending on thickness).
Transfer steak to a cutting board, season with additional salt and pepper, and allow to rest for 10 minutes. Slice thinly across the grain and transfer to a large bowl. Toss with 3 Tablespoons of the vinaigrette.
To Serve: Mound or arrange slices of steak on top of salad, sprinkle with peanuts and serve with additional dressing on the side.
Notes
*If you can not find Thai Basil, do not substitute it with regular basil. Simply replace it with mint.