Preheat your oven to 400°F. Halve the baby potatoes, toss them with olive oil and a pinch of salt, and roast on a sheet pan for 20 minutes until golden.
Pat the flank steak completely dry with paper towels and season both sides with the sea salt and black pepper.
Heat a large cast-iron skillet over medium-high heat until it is very hot.
Place the steak in the skillet and sear for 4 to 5 minutes per side for medium-rare doneness.
In the last 2 minutes of cooking, add the ghee, smashed garlic cloves, and fresh rosemary to the skillet.
Tilt the pan slightly and use a large spoon to continuously baste the steak with the melted garlic butter.
Transfer the steak to a cutting board and let it rest for 10 minutes to allow the juices to redistribute.
While the steak rests, add the asparagus to the same skillet and sauté in the remaining pan juices for 3 to 4 minutes until crisp-tender.
Slice the steak thinly against the grain and serve immediately with the roasted potatoes and asparagus.