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 of the sea salt and black pepper.
Heat olive oil in a large skillet over medium-high heat and cook the chicken until golden and cooked through, then remove and slice into strips.
In the same skillet, add the sliced mushrooms and shallots, sautéing until the mushrooms have released their moisture and turned golden brown.
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 from the bottom.
Drain the pasta, reserving a small amount of pasta water, and add the noodles to the skillet with the mushrooms.
Add the sliced chicken back to the pan along with the truffle oil, parmesan cheese, and remaining salt and pepper.
Toss everything together until the pasta is coated in a light sauce, adding a splash of pasta water if needed for silkiness.
Garnish with fresh parsley and serve immediately.