In a shallow roasting pan, toss potatoes with ½ tablespoon of the oil, sage leaves, and salt. Roast 22 to 25 minutes, tossing occasionally, until crisp and golden.
Meanwhile, in a small saucepan, boil beef broth until broth is reduced to ½ cup, 10 to 12 minutes. Stir in Dijon mustard and set aside.
Trim fat from steaks. Cut each steak in half. Flatten between plastic wrap to about ¼-inch thickness. Rub steak with soy sauce and ½ tablespoon of the oil.
In a large nonstick skillet, heat remaining 1 tablespoon oil over high heat. Add butter, swirling pan to coat. Add 2 pieces of steak; sear 1 minute per side for medium rare. Remove to a platter. Repeat with remaining 2 pieces of steak; transfer to platter.
Add shallot to drippings in skillet and saute 30 seconds. Pour in broth mixture, parsley, Worcestershire sauce, and lemon juice. Spoon sauce over steaks and serve with roasted potatoes.
447 calories (38g protein, 22g carbohydrate, 23g fat) per serving