Preheat your oven to 400°F (200°C).
Dice the Yukon gold potato into 1/2-inch cubes and place them on a parchment-lined baking sheet.
Melt 1 teaspoon of ghee and toss it with the potatoes, dried rosemary, and a pinch of salt and pepper.
Roast the potatoes for 15 minutes.
Add the broccoli florets to the baking sheet, toss with the potatoes, and roast for an additional 10-12 minutes until the vegetables are tender and slightly charred.
While the vegetables roast, season the sirloin steak on both sides with the remaining salt and pepper.
Heat a cast-iron skillet over medium-high heat and add the remaining 1 teaspoon of ghee.
Place the steak in the hot skillet and sear for 3-4 minutes per side for medium-rare.
During the last 2 minutes of cooking, add the minced garlic and dried thyme to the pan, spooning the melted herb ghee over the steak.
Remove the steak from the pan and let it rest for 5 minutes before slicing against the grain.
Serve the sliced steak alongside the roasted potatoes and broccoli.