Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Cut the Yukon gold potato into 1/2-inch cubes and toss them in a bowl with the extra virgin olive oil, dried rosemary, and a pinch of salt and pepper.
Spread the potatoes in a single layer on the baking sheet and roast for 20-25 minutes until the edges are crispy and golden.
While the potatoes roast, cut the sirloin steak into 1-inch cubes and pat them thoroughly dry with a paper towel to ensure a good sear.
Season the steak bites evenly with the remaining sea salt and black pepper.
Heat a large cast-iron skillet over medium-high heat until it is very hot, then add the steak bites in a single layer without overcrowding.
Sear the steak for 2 minutes undisturbed to develop a deep crust, then flip and cook for another 1-2 minutes for medium-rare.
Reduce the heat to medium, add the ghee and minced garlic to the skillet, and toss the steak bites for 60 seconds until they are glossy and fragrant.
Remove the skillet from the heat and serve the steak bites immediately alongside the roasted potatoes, garnished with freshly chopped parsley.