Prepare the Sauce: In a bowl, combine all the sauce ingredients. Whisk well and set aside.
Taste and Adjust: Give the sauce a taste. If you prefer it sweeter, you can add a bit more maple syrup or agave. If you like it saltier, add a touch more soy sauce or tamari. For more heat, increase the amount of chili paste or sriracha.
Prepare Noodles: Cook the yakisoba noodles according to the package instructions. Once cooked, drain, and rinse with cold water. Set aside.
Cook the Tofu: Heat a tablespoon of oil in a large pan or wok over medium heat. Add the tofu cubes and cook until golden brown on all sides. Once done, transfer the tofu to a plate and set aside.
Sauté the Veggies: In the same pan, add your choice of vegetable, stir-fry for about 4-5 minutes, or until the vegetables are tender yet still crisp.
Combine Noodles, Tofu, and Sauce: Add the cooked noodles and tofu back into the pan with the veggies. Pour the vegan yakisoba sauce over everything. Toss well to combine, ensuring the sauce coats everything evenly. Stir-fry for another 2-3 minutes to heat everything through and allow the flavors to meld.
Serve: Dish out the yakisoba onto plates or bowls. Garnish with sliced green onions, a sprinkle of sesame seeds, and nori flakes if desired.