Bring a large pot of salted water to a boil and cook the tagliatelle according to package directions until al dente.
While the pasta cooks, slice the chicken breast into thin strips and season with half of the sea salt and black pepper.
Heat the olive oil in a large skillet over medium-high heat and sauté the chicken until golden and cooked through, then remove from the pan and set aside.
In the same skillet, add the sliced mushrooms and cook until they release their moisture and begin to brown, about 5 minutes.
Add the minced garlic to the mushrooms and sauté for 1 minute until fragrant.
Reserve 0.25 cup of pasta water, then drain the tagliatelle.
Add the cooked pasta, chicken, and reserved pasta water to the skillet with the mushrooms, tossing everything together over low heat.
Drizzle with the truffle oil and toss again to coat evenly.
Serve immediately topped with grated parmesan cheese, fresh parsley, and the remaining salt and pepper.