Bring a large pot of water to a boil.
Add the noodles and cook them according to the package directions.
Drain the noodles into a colander, rinse them with cold water, and then return them to the pot. Toss the noodles with a dash of oil to prevent sticking.
Whisk the soy sauce, mushroom soy sauce, hoisin sauce, brown sugar, cornstarch, and sesame oil together in a small bowl, making sure to dissolve the sugar.
Place a large skillet or wok with a nonstick surface over medium heat. Add 3 tablespoons of oil to the skillet.
Give the oil a few minutes to heat up, and then add the noodles, arranging them in a relatively even layer.
Fry the noodles in the oil for about 2 minutes until they begin to crisp on the bottom, then use a fork or spatula to redistribute the noodles. Continue cooking and redistributing the noodles every 2 minutes or so, until they have lots of crispy spots. This should take a total of about 8 minutes.
Remove the noodles from the skillet and transfer them to a plate.
Add the remaining tablespoon of oil to the skillet. Give it a minute to heat up, then add the mushrooms.
Let the mushrooms cook for about 4 minutes, until they begin to soften up and brown on the bottoms.
Push the mushrooms to the side and add the garlic, ginger, and white parts of scallions to the skillet. Cook the aromatics for about 1 minute, until very fragrant, being careful to avoid burning.
Raise the heat to high and add the carrots and celery to the skillet. Stir-fry the veggies until they brighten in color slightly, about 2 minutes.
Add the cabbage and continue to stir-fry for about 1 minute, until it just begins to soften.
Return the noodles to the skillet and add the soy sauce mixture. Use a fork or spatula to distribute the ingredients, making sure to get an even coating of the sauce on the noodles.
Remove the skillet from the heat and stir in the green parts of the scallions.
Divide onto plates and serve.