1. In a medium bowl, whisk together the mirin, 1 teaspoon salt and 1 teaspoon pepper. Add the steaks, turning to coat evenly, then refrigerate for at least 20 minutes and up to an hour.
2. When ready to cook, in a large skillet over medium-high, heat the oil until very hot but not smoking. Add the steaks and sear on each side for 1 1/2 minutes. Transfer the steaks to a platter and let rest for 5 minutes.
3. Once the steaks have rested, thinly slice them across the grain. Fan the slices onto 2 serving plates, then seasoned with salt and pepper. Squeeze 1 or 2 lemon wedges over each. Serve immediately.
Nutrition information per serving: 290 calories; 90 calories from fat (31 percent of total calories); 10 g fat (1.5 g saturated; 0 g trans fats); 105 mg cholesterol; 7 g carbohydrate; 0 g fiber; 5 g sugar; 37 g protein; 570 mg sodium.