Soak shiitake mushrooms in boiling water for 15 minutes to soften.

Grate firm tofu using a box grater or food processor.

Slice moonlight mushrooms, mince garlic, and chop onion.

Bring a large pot of salted water to a boil for the pasta.

Sauté onion, garlic, salt, and pepper in vegetable oil until translucent (about 7 minutes).

Stir in sliced mushrooms and grated tofu and cook until mushrooms release their juices (about 5 minutes).

Remove softened shiitake mushrooms from the bowl, discard large stems, and slice the caps.

Add shiitake mushroom slices to the skillet.

Add 3/4 cup of the shiitake soaking liquid, being careful to avoid any gritty residue.

Add sweet bean sauce and vinegar; stir occasionally until the sauce is hot (about 5 minutes).

If the sauce is too thick, add a little water.

Cook pasta until al dente while the sauce simmers.

Prepare the toppings.

Drain the pasta.

Serve noodles in individual bowls, topped with sauce and desired toppings.