How to Make It
In a small saucepan, combine the mirin and vinegar with the water and 1 teaspoon of kosher salt; bring to a boil. Add the rice and bring to a boil. Cover and cook over low heat for 22 minutes, or until the liquid is absorbed and the rice is just tender. Stir in the minced ginger, black beans and sliced scallions.
Preheat the oven to 400°. Line six 1/2-cup ramekins or standard-size muffin cups with plastic wrap, then pack them with the warm rice and let cool.
Season the steak with salt and pepper. Heat 2 tablespoons of the oil in a medium skillet. Add the steak and cook over moderately high heat until well browned on both sides, about 8 minutes. Transfer the steak to a rimmed baking sheet and roast for 20 minutes, or until an instant-read thermometer inserted in the center of the steak registers 130° for medium-rare. Transfer the steak to a cutting board and let rest for 5 minutes.
Meanwhile, heat the remaining 1 tablespoon of vegetable oil in a large nonstick skillet. Unmold the rice cakes and fry them over moderately high heat until they are golden brown and crisp, turning once, about 2 minutes. Thickly slice the steak against the grain and serve with the rice cakes and hoisin sauce.