6 tablespoons Tamari (dark soy sauce) or liquid amino, such as Bragg, divded
4 tablespoons mirin, divded
4 tablespoons canola oil, divded
1 tablespoon Worcestershire sauce
2 large cloves garlic, grated or finely chopped
1 1/2 pounds flatiron steak, about 1 1/2 inches thick, at room temperature
1 cup beef stock
3/4 pound shiitake mushrooms, stemmed and thinly sliced
12 scallions-trimmed, cut into 3-inch pieces and sliced lengthwise
10-12 ounces soba noodles
1 package enoki mushrooms (5 ounces), bottoms trimmed and mushrooms separated
A fat handful of green or red shiso leaves or red leaf lettuce, shredded
Gomasio (sesame salt) or toasted white or black sesame seeds
In a shallow dish, combine 2 tablespoons Tamari, 1 tablespoon mirin, 2 tablespoons oil, the Worcestershire saice and the garlic. Add the steak and turn to coat; season with pepper. Heat a grill pan or griddle over medium heat. Add the steak and cook, turning occasionally, to desired doneness, 8-10 minutes for medium-rare. Transfer to a cutting board and let rest 5 minutes. Meanwhile, bring a large pot of water to a boil. In a small pot, over medium heat, warm the stock and the remaining 4 tablespoons Tamari and 3 tablespoons mirin. In a large skillet, heat the remaining 2 tablespoons oil over high. When the oil starts to smoke, add the shiitakes and cook until brown, then add the scallions and toss to combine.
Cook the soba in the boiling water until tender. Drain and rinse with cold water, then return the soba to the pot. Add the cooked shiitakes, the enoki mushrooms and the sauce; stir to heat through. Divide the soba among plates, then top with the shiso and gomasio. Thinly slice the steak crosswise against the grain. Serve with the soba.