- Rub skirt steak well with about 1 tablespoon olive oil oil, steak seasoning, and kosher salt. Let rest while you preheat your pan or grill to medium-high heat.
- Slice focaccia roll in half and drizzle cut side with olive oil (1 tablespoon per side). Add focaccia to your grill or skillet, olive oil side down, and toast for a few minutes.
- Remove focaccia and add skirt steak. Cook skirt steak on the grill or in a sturdy cast iron skillet for 4-5 minutes per side. The steak should reach an internal temperature of at least 140˚ F. When steak is cooked through, remove it from the heat and let rest until it has cooled off and is just warm.
- Meanwhile, slice up cucumbers, shallots, and mix up the mayo.
- Slather bottom roll with a few tablespoons of lemon parsley mayo. Top with arugula, sliced cucumbers, and shallot.
- Slice skirt steak against the grain and then pile on to the sandwich.
- Slather top piece of focaccia with more mayo and add to sandwich. Press the sandwich down and slice it into hand-sized pieces. I use a square focaccia and cut mine into 9 even pieces.
Serve sandwiches right away or wrap tightly and store in the fridge for 24 hours.