Bring a medium pot (large pot for 4 servings) of water to a boil. Wash and dry produce.

Trim and and thinly slice mushrooms (skip if your mushrooms are pre-sliced!). Trim scallions; cut whites into 1-inch pieces and thinly slice greens. Peel and mince or grate ginger.

Once water is boiling, add noodles to pot. Cook, stirring occasionally, until al dente, 5-7 minutes. Reserve ¼ cup noodle cooking water (½ cup for 4 servings); drain and set aside.

While noodles cook, in a small bowl, whisk together stock concentrate with ⅓ cup warm water (⅔ cup for 4). Add soy sauce, sesame oil, garlic powder, 3 TBSP sugar, and 2 tsp vinegar (6 TBSP sugar and 4 tsp vinegar for 4). (Be sure to measure the vinegar—we sent more!) Stir to combine.

Heat a large drizzle of oil in pot used for noodles over medium-high heat. Add mushrooms and scallion whites. Cook, stirring occasionally, until veggies are browned, 3-4 minutes.

Add carrots and a pinch of salt; cook, stirring occasionally, until softened, 1-2 minutes. Add ginger and cook, stirring, until fragrant, 30-60 seconds. 

Reduce heat under pot with veggies to medium. Add spinach, bok choy and napa cabbage, soy-garlic sauce, drained noodles, and reserved noodle cooking water. Cook, stirring occasionally, until sauce has thickened, 1-2 minutes.

Divide lo mein between bowls. Sprinkle with scallion greens and serve.