Heat some oil in a pan (optional) and cook the tofu over medium-high heat for 5-10 minutes or until golden brown. Reserve.
After that, cook the sauce. Add all the ingredients for the sauce into a saucepan, stir and bring to a boil. Simmer for 5 minutes or until it thickens a little. Remove from heat and set aside.
Soak the noodles for 30-60 minutes in water at room temperature or in hot water for 5 minutes (that's what I usually do). Drain and reserve.
Heat 1 tablespoon of oil in a wok or pan and cook the onion and garlic over medium-high heat for 2-3 minutes or until golden brown, stirring frequently.
Incorporate the noodles, tofu, fresh bean sprouts, and chives, stir and cook for 1-2 minutes.
Add the sauce, mix until well combined and cook for 2-3 more minutes.
Serve with chopped peanuts, some more fresh bean sprouts, chives (optional), lime juice, and cayenne flakes on top.
Keep the leftovers in an airtight container in the fridge for 4-5 days.
Notes
You can substitute tofu for any other vegan meat or even mushrooms.
Feel free to incorporate all your favorite veggies, such as carrots or red bell peppers.
Use any sweetener you'd like.
Vegan fish sauce can be replaced by tamari or soy sauce, although this recipe works best with vegan fish sauce.
I'd recommend you make this vegan pad Thai with tamarind paste, but if you can't find it you could use lime or lemon juice instead.