Preheat your grill or grill pan over medium-high heat.

Rub the flank steak with vegetable oil, salt, and black pepper.

Grill the steak for about 4-5 minutes per side for medium-rare, or until it reaches your desired doneness.

Remove from the grill and let it rest for 5-10 minutes before slicing thinly against the grain.

In a large bowl, combine the salad greens, cherry tomatoes, cucumber, red bell pepper, red onion, cilantro, mint, and peanuts if using.

In a small bowl, whisk together lime juice, fish sauce, soy sauce, brown sugar, garlic, ginger, and red pepper flakes until the sugar is dissolved.

Add the sliced steak to the salad and drizzle with the dressing.

Toss gently to combine and serve immediately.