Rinse the green asparagus and remove the tough ends. Finely chop the parsley and garlic. Mix this in a bowl with the vinegar, chili flakes, salt, pepper and half of the olive oil to make a chimichurri. Set the mixture aside and season the steak on both sides with salt and pepper.
Heat a pan over medium-high heat. Roast the asparagus in the remaining olive oil until they are colored all over and tender-crisp. Remove the vegetables from the pan and keep them warm.
Turn the heat under the same pan to high. Sear the steak quickly and firmly, about two minutes per side for a medium-rare result. Remove the meat from the pan and let it rest for five minutes on a cutting board.
Slice the steak into thin slices. Divide the roasted asparagus over the plates and lay the meat on top or beside it. Generously spoon the chimichurri over the steak and serve immediately.