In a medium saucepan, cover the potatoes with water and bring to a boil.
Reduce the heat and simmer for 10-15 minutes, or until just tender.
Drain, and toss with the olive oil, vinegar, mustard, green onion, parsley, salt and pepper while still warm.
Meanwhile, season the steaks with salt. Set a heavy (cast iron is ideal) skillet over medium-high heat.
Drizzle some oil into the skillet and when it’s hot, cook the steaks for about 4 minutes, until a deep crust has developed on the bottom.
Flip and cook for another 4-5 minutes (for medium-rare) or until done to your liking.
Let the steaks rest for 5-10 minutes before slicing and serving with the warm potato salad.