Wash and dry all produce. Preheat oven to 425 degrees. Halve potatoes lengthwise. (TIP: Quarter any large ones so they cook evenly.) Strip and finely chop enough rosemary from stems to give you 1 TBSP. Toss potatoes, rosemary, and a drizzle of oil on a baking sheet. Season with salt and pepper.

Roast potatoes in oven until browned, about 25 minutes total (we’ll add more to the sheet after 10 minutes). Halve, peel, and finely chop shallot. Pick and roughly chop enough tarragon leaves from stems to give you 1 TBSP. Trim woody bottom ends from asparagus.

Heat a drizzle of oil in a medium pan over medium-high heat. Pat steak dry with a paper towel and season all over with salt and pepper. Add to pan and cook to desired doneness, 3-6 minutes per side. Remove from pan and set aside to rest. Reduce heat to medium low.

After potatoes have roasted for 10 minutes, remove from oven and toss, pushing toward one side of baking sheet. Add asparagus to other side of sheet, toss with a drizzle of oil, and season with salt and pepper. Return sheet to oven and continue roasting until asparagus is tender and lightly browned and potatoes are done, 10-15 minutes.

Add shallot to pan used for steak. Cook, tossing, until just softened, 1-2 minutes. Pour in vinegar and scrape up any browned bits on bottom. Add chopped tarragon. Cook until vinegar evaporates, about 1 minute. Stir in 1/2 cup water and stock concentrate. Bring to a boil, then lower heat and simmer until reduced by half, 2-3 minutes. Remove from heat. Stir in 2 TBSP butter. Season with salt and pepper.

Slice steak against the grain. Divide potatoes, asparagus, and steak between plates. Spoon sauce over steak and serve.