1 lb. peeled baking potatoes, cut into ¼”-thick strips
1 tsp. extra-virgin olive oil
1 tsp. chopped fresh rosemary
½ tsp. sea salt, divided
¼ cup red wine vinegar
1 Tbsp. whole-grain Dijon mustard, plus more for serving
2 tsp. coarse black pepper
2 tsp. chopped fresh thyme
1 lb. lean flank steak (all fat removed)
2 tsp. freshly minced parsley, for garnish

Preheat oven to 450.  Coat a baking sheet with cooking spray.

Toss potatoes with oil; add rosemary and ¼ tsp. sea 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 ¼ tsp. 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.