Heat the olive oil in a large pan over medium-high heat. Add the diced onion and saute until lightly browned, about 3-4 minutes.
Add the garlic and cook for another 1 minute.
Then add the sliced fresh shiitake mushrooms. Saute until tender and cooked through.
Add the soy sauce and ground black pepper. Remove from heat.
Bring a large pot of water a to a boil. Add the pasta and cook according to directions on the package.
Once the pasta is cooked, use tongs to move the noodles from the pot to the pan with the mushrooms. Add in about a half-cup of the pasta water to the pan.
Over medium-low heat, gently toss the pasta with the mushrooms. The starchy pasta water will help bind the sauce to the noodles. Cook for another minute until well combined.
Divide between two plates. Eat and enjoy! ^_^