1 pound Yukon gold potatoes, cut into 2-inch pieces
1/2 pound parsnips (about 2 medium), cut into 1-inch pieces
kosher salt and black pepper
1/2 C. whole milk
2 T. butter
2 scallions, thinly sliced
1 T. olive oil
1 1/2 pounds sirloin steak (1 inch thick)

Place the potatoes and parsnips in a large pot. Cover with cold water and bring to a boil. Add 2 tsp. salt, reduce heat, and simmer until tender, 15 to 18 minutes. Drain and return to the pot. Mash with the milk, butter, scallions, 1⁄2 tsp. salt, and 1⁄4 tsp. pepper. Meanwhile, heat the oil in a large skillet over medium-high heat. Season the steak with 1⁄2 tsp. each salt and pepper. Cook to the desired doneness, 4 to 6 minutes per side for medium-rare. Let rest before slicing. Serve with the potato-parsnip mash.