Cook the yakisoba noodles according to the package directions, then drain and let them cool.

In a medium-sized saucepan, combine brown sugar, soy sauce, rice vinegar, grated garlic, and ginger. Stir until the brown sugar is completely dissolved, then bring the sauce to a simmer.

Create a slurry by whisking together the canned pineapple juice and cornstarch.

Add the pineapple juice and cornstarch slurry to the simmering sauce. Bring it back to a boil and let it reduce for 10 minutes.

While the sauce is reducing, heat a few tablespoons of oil in a wide pan. Sauté the vegetables until they become tender and slightly caramelized. Then, set them aside.

Strain the sauce through a fine mesh strainer to remove the garlic and ginger. Discard the garlic and ginger.

Add the cooled noodles to the sautéed vegetables, mixing them together.

Pour ¾ of the sauce over the noodles and vegetables. Toss to combine, and taste to adjust the flavor, adding more sauce if needed.

Garnish the dish with sliced scallions and crushed peanuts.