Preheat your oven to 425°F and line a baking sheet with parchment paper.
Slice the russet potato into thin, even fries and pat them thoroughly dry with a paper towel to ensure maximum crispiness.
Toss the potato fries with olive oil and a pinch of sea salt, then spread them in a single layer on the baking sheet.
Roast the fries for 20 to 25 minutes, flipping halfway through, until they are golden brown and crispy.
Season both sides of the sirloin steak with the remaining sea salt and black pepper.
Heat the ghee in a cast-iron skillet over medium-high heat until it begins to shimmer.
Sear the steak for 3 to 4 minutes per side for medium-rare, then remove from the pan and let it rest on a cutting board for 5 minutes.
While the steak rests, finely mince the garlic and parsley, then toss them with the hot fries and parmesan cheese in a large bowl.
Slice the steak against the grain and serve immediately alongside the hot garlic parmesan fries.