Drizzle steak with oil and sprinkle liberally with salt and pepper; rub to coat. Transfer to a preheated grill on high heat. Grill steak, flipping as needed, until charred and a meat thermometer reads 125F when inserted into the thickest part of the meat. Remove from grill and tent with foil; rest for at least 10 minutes. Slice steak against the grain as thinly as possible. Then cut into small pieces for assembly.

In a bowl, stir together mayonnaise and mustard. Scrape into a zipper bag. Snip the corner of the bag for piping.

Assembly: Top each chip with a piece of steak, and a small dollop of Dijon mayo; sprinkle with sliced chives. Serve immediately.