Homemade oils infused with rosemary and garlic marry with steak juices to make a fragrant pan sauce. Chill and save the extra rosemary oil to spoon over grilled chicken or vegetables.
- 3/4 cup plus 7 Tbsp. olive oil, divided
- 1/4 cup 1-inch pieces rosemary sprigs
- 1 1/2 pounds hanger or flank steaks, cut into four 6-ounce steaks
- Kosher salt, freshly ground pepper
- 6 large garlic cloves, sliced
- Coarse sea salt
Heat 3/4 cup oil and rosemary in a small saucepan over medium heat until oil begins to bubble and an instant-read thermometer registers 140°, about 2 minutes. Let steep at room temperature for at least 2 hours or cover and chill overnight (the longer it steeps, the more flavorful it will be). Strain oil; discard rosemary. Set rosemary oil aside.
Rub steaks with 1 Tbsp. olive oil; season generously with kosher salt and pepper. Heat 2 Tbsp. oil in a large heavy skillet over high heat until it begins to shimmer. Quickly sear steaks on all sides and transfer to a cutting board (they will still be quite rare; you’ll finish cooking them shortly). Let rest for 10 minutes. Clean and dry skillet.
Cook remaining 4 Tbsp. oil and garlic in skillet over medium heat, turning occasionally, until garlic is dark brown but not burnt, 3–4 minutes. Remove pan from heat; discard garlic. Transfer 2 Tbsp. garlic oil to a small bowl; reserve.
Cut steaks against the grain into 1/3-inch-thick slices. Heat remaining garlic oil in skillet over medium heat until it shimmers. Add half of sliced steak to skillet and cook, turning once, until cooked to desired doneness, 1–2 minutes for medium-rare. Add 1 Tbsp. rosemary oil; toss. Transfer steak and oil to a platter. Repeat with reserved garlic oil, steak, and 1 Tbsp. rosemary oil.
Sprinkle with sea salt and drizzle with more rosemary oil, if desired.