Grilled Beef Sirloin Recipe

Prep and soak

Peel (optional) and cut the russet potatoes into 1/4–1/2-inch sticks. Place the cut fries in a large bowl of cold water and soak for at least 30 minutes (or up to 2 hours) to remove excess starch. Drain and rinse, then pat completely dry with clean kitchen towels or paper towels.

Par-cook (optional oven method)

If baking/oven-roasting: preheat oven to 425°F (220°C). Toss dried fries with 1–2 tsp oil and 1 tsp cornstarch for extra crisp, spread in a single layer on a parchment-lined sheet, and roast 20–30 minutes, turning once, until golden and crisp. Season with salt and pepper immediately.

Deep-fry method

If deep-frying: heat neutral oil in a heavy pot or fryer to 325°F (160°C). Fry potatoes in batches for 4–5 minutes until pale and slightly tender but not browned. Remove and drain on a rack. Increase oil temperature to 375°F (190°C) and fry batches again for 2–3 minutes until golden and crisp. Drain, then season with 1 tsp kosher salt and 1/2 tsp black pepper while hot.

Heat a large skillet over medium heat. Add 1 tablespoon olive oil and 1 teaspoon butter. When the butter melts and the oil shimmers, add the thinly sliced garlic and sauté for 20–30 seconds until fragrant but not browned.

Add the baby spinach in batches, allowing it to wilt before adding more. Toss frequently with tongs until just wilted, about 2–3 minutes total.

Season with 1/2 teaspoon salt, 1/4 teaspoon freshly ground black pepper, 1 teaspoon lemon juice, and the optional pinch of red pepper flakes. Toss to combine, remove from heat, and keep warm until plating.

Bring the 1 lb sirloin steak to room temperature for 20–30 minutes before cooking. Pat the steak dry with paper towels.

Season both sides of the steak evenly with 1 tsp kosher salt, 1/2 tsp black pepper, and 1/2 tsp garlic powder. Lightly rub 1 tablespoon olive oil over the surface to help seasoning adhere.

Preheat a grill, grill pan, or heavy skillet (cast iron) over high heat until very hot (a drop of water should sizzle and evaporate). If using a skillet, add it dry or with a thin film of oil.

Place the steak on the hot grill or pan. For a 1-inch-thick sirloin, grill 4–5 minutes per side for medium-rare (internal temperature 130–135°F / 54–57°C). Adjust time for thickness and desired doneness: about 3–4 minutes per side for rare, 6–7 minutes per side for medium. Do not constantly flip—turn once.

During the last minute of cooking, add 1 tablespoon unsalted butter, the 1 crushed garlic clove, and the thyme sprigs to the pan (or brush butter on the steak if using a grill). Tilt the pan and use a spoon to baste the steak with melted butter and aromatics for extra flavor.

Remove the steak from heat and transfer to a cutting board. Tent loosely with foil and rest for 5–8 minutes to allow juices to redistribute.

Slice the steak against the grain into 1/4-inch slices. Serve alongside the sautéed spinach and fries, spooning any resting juices or pan-basting butter over the sliced steak.