Wash and dry all produce. Preheat oven to 425 degrees. Peel parsnips, then cut into 3-inch-long pieces. Halve each piece lengthwise, then cut into thin wedges. Strip rosemary leaves from stems. Discard stems and chop leaves. Thinly slice garlic crosswise.

On a baking sheet, toss parsnips, a drizzle of oil, half the rosemary, and a pinch of salt and pepper. Roast in oven until lightly browned, 20-25 minutes, tossing halfway through.

Heat a drizzle of oil in a large pan over medium-high heat. Season steak all over with salt and pepper. Add to pan and cook until it almost reaches desired doneness, 3-6 minutes per side.

Reduce heat to low and add 2 TBSP butter, remaining rosemary, and half the garlic to pan. Tilt pan toward you to collect melted butter. Using a spoon, continuously spoon butter, garlic, and rosemary over steak until it reaches desired doneness, 1-2 minutes. Remove steak from pan and let rest 5 minutes. TIP: Loosely cover steak with aluminum foil to keep warm.

Increase heat under same pan to medium. Add remaining garlic and cook until fragrant, 30 seconds. Add spinach and toss until wilted, 3-4 minutes. (TIP: Add a splash of water if you’re having trouble getting spinach to wilt.) Remove pan from heat and let cool 1 minute. Stir in sour cream. Season with salt and pepper.

Slice steak against the grain. Divide parsnips, steak, and spinach between plates and serve.