Cook the spaghetti according to package directions until al dente, drain and set aside.
While the pasta cooks, slice the mushrooms, cut green onions into 1/2-inch pieces, and cut carrots into matchsticks or shred/dice if you prefer; mince the garlic and grate ginger if using.
Heat a large skillet or wok over medium-high heat and add 3 tablespoons water or broth for a no-oil sauté, or 2 teaspoons toasted sesame oil for more flavor.
Sauté the sliced mushrooms for 2–3 minutes until they begin to soften.
Add the snow peas, carrots, and green onions to the pan and cook for about 5 minutes until the vegetables are crisp-tender.
Reduce the heat to medium and add the minced garlic and grated ginger (if using); stir and cook for about 1 minute until fragrant.
Add the drained spaghetti and tamari to the skillet, starting with less tamari if you prefer (2–3 Tbsp.), and toss well to combine and heat through for 2–3 minutes.
Remove from heat, top with sesame seeds and mung bean sprouts if desired, and serve warm or chilled.
