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, season the chicken breast with half the salt and pepper, then pan-sear in a non-stick skillet over medium-high heat until cooked through.
Remove the chicken from the skillet, let it rest for two minutes, and then slice into thin strips.
In the same skillet, heat the olive oil over medium heat and sauté the shallots and mushrooms until the mushrooms are golden and tender.
Add the minced garlic to the skillet and cook for 30 seconds until fragrant.
Pour in the chicken broth to deglaze the pan, scraping up any browned bits, and simmer for 2 minutes to slightly reduce.
Toss the cooked pasta and sliced chicken into the skillet with the mushroom mixture until well combined.
Drizzle with truffle oil and sprinkle with the remaining salt, pepper, and fresh parsley.
Serve immediately topped with the grated parmesan cheese.