Step 1

In a large (at least 8-quart) pot, bring 5 quarts water to a boil. Add the noodles, shaking them over the baking sheet to remove excess starch. Cook, stirring occasionally, until a noodle rinsed under cold water is tender, 10 to 15 minutes. Drain in a colander, rinse under cold water and drain again.

Step 2

While the noodles cook, thinly slice the cucumber on the diagonal. Stack several slices and cut lengthwise into matchsticks. Repeat with the remaining slices. Set the cucumber aside. Meanwhile, in a small bowl, stir together the cornstarch and 2 tablespoons water; set aside.

Step 3

In a large Dutch oven over medium-high, heat the sesame oil until shimmering. Add both ground meats and cook, stirring and breaking the meat into small pieces, until browned, 4 to 5 minutes. Add the mushrooms, bamboo shoots (if using), garlic and ginger; cook, stirring, until fragrant, 1 to 2 minutes. Stir in the broth, sake, chili-bean sauce, miso, soy sauce and mirin. Bring to a simmer, then reduce to medium and cook until the liquid has reduced by half, 6 to 7 minutes.

Step 4

Stir the cornstarch slurry to recombine, then stir it into the meat-mushroom mixture. Cook, stirring constantly, until the sauce returns to a simmer and has thickened, about 1 minute. Add the noodles, toss well and cook, stirring, just until the noodles are heated through, 2 to 3 minutes. Serve topped with scallions and cucumber.