Preheat your oven to 400°F and line a baking sheet with parchment paper.
Toss the cubed sweet potato with half of the olive oil and a pinch of sea salt and pepper.
Roast the sweet potatoes for 20-25 minutes until they are tender and slightly crispy on the edges.
Pat the sirloin steak completely dry with paper towels and season both sides generously with sea salt and black pepper.
Heat a cast-iron skillet over medium-high heat with the remaining olive oil until the pan is shimmering.
Place the steak in the hot skillet and sear for 3-4 minutes per side for medium-rare doneness.
During the last 2 minutes of cooking, add the ghee, smashed garlic clove, rosemary, and thyme to the skillet.
Tilt the pan slightly and use a large spoon to continuously baste the foaming herb ghee over the steak.
Remove the steak from the pan and let it rest on a cutting board for at least 5 minutes to lock in the juices.
In the same skillet, sauté the broccolini for 3-5 minutes until it is bright green and develops a slight char.
Slice the steak against the grain and serve alongside the roasted sweet potatoes and charred broccolini.