Sauté the aromatics: Heat the oil in a large pot over medium heat.
Add the onion and a pinch of salt. Cook 3–4 minutes until softened. Stir in the garlic and ginger and cook for 30 seconds until fragrant.
Add the vegetables: Add carrots, celery, mushrooms, zucchini, and green beans.
Cook 5–6 minutes, stirring occasionally, until the vegetables begin to soften and the mushrooms release some liquid.
Build the broth: Pour in the broth. Add soy sauce (if using), thyme, and the bay leaf. Bring to a gentle boil, then reduce to a simmer.
Taste and season with salt and pepper as needed.
Simmer to meld flavors: Let the soup simmer for 10 minutes, until the carrots are tender but not mushy. If adding cooked chicken or tofu, stir it in now to warm through.
Cook the noodles: You have two options. For the best texture, cook egg noodles separately in salted water according to package directions, then drain.
Or, add noodles directly to the soup and cook until just tender. Either way, avoid overcooking.
Finish with greens and brightness: Stir in the spinach (or kale) and let it wilt, 1–2 minutes. Add lemon juice or rice vinegar to brighten the flavor.
Adjust salt, pepper, and seasonings to taste.
Serve and garnish: Ladle into bowls. Add noodles if you cooked them separately. Garnish with chopped parsley or green onions.
Drizzle a little sesame oil or sprinkle red pepper flakes if you like heat.