1 pound peeled baking potatoes, cut into 1/4-inch-thick strips
1 teaspoon extra-virgin olive oil
1 teaspoon chopped fresh rosemary
3/4 teaspoon sea salt, divided
1/4 cup red wine vinegar
1 tablespoon whole-grain Dijon mustard, plus more for serving
2 teaspoons coarse black pepper
2 teaspoons chopped fresh thyme
1 pound lean flank steak
2 teaspoons freshly minced parsley, for garnish
How to Make It
Preheat oven to 450°. Coat a baking sheet with cooking spray.
Toss potatoes with oil; add rosemary and 1/2 teaspoon salt. Place in a single layer on baking sheet. Bake 20–22 minutes or until golden, tossing halfway through. Remove from oven, and gently loosen with a spatula; keep warm.
Place oven rack at highest position; preheat broiler. Coat a broiler pan with cooking spray.
Whisk together the vinegar, mustard, pepper, thyme, and remaining 1/4 teaspoon salt in a large dish. Add steak; marinate at room temperature 20 minutes, turning occasionally. Broil for 6–7 minutes per side or to desired degree of doneness. Remove from oven; let stand for 5 minutes. Cut into 4 equal portions.
Divide steak and fries evenly among plates. Garnish with parsley, if desired. Serve immediately with mustard.