Kosher salt and freshly ground black pepper, to taste
1 tablespoon extra-virgin olive oil, plus more to season
Pan-sear hanger steak: Preheat cast-iron skillet over medium-high heat until hot.
Just before cooking, pat steak dry with paper towels and sprinkle with kosher salt and pepper.
Add oil to hot skillet then add steak. Cook steak for about 4 minutes per side, or until dark brown on the bottom and internal temperature reaches 130 degrees. Transfer steaks to a rack set on a baking sheet and let rest for 5 minutes.
Grill broccolini: Preheat a grill pan to medium-high heat.
Toss broccolini in large bowl with salt, pepper and 1 tablespoon oil.
Grill broccolini until stems are crisp yet tender and leaves begin to char, about 3 to 4 minutes per side. Remove broccolini from grill and season to taste with a touch of oil and salt and pepper.
Serve: Slice steaks against grain. Divide steak between 2 plates. Sprinkle with sea salt flakes. Serve immediately with broccolini.