Boil a large pot of salted water and cook the tagliatelle according to package directions until al dente, reserving 0.25 cup of pasta water before draining.
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 sear the chicken for 6 minutes per side until fully cooked, then slice into thin strips.
In the same skillet, sauté the sliced mushrooms and minced garlic for 5 minutes until the mushrooms are golden and fragrant.
Reduce the heat to low and add the cooked pasta, sliced chicken, Greek yogurt, reserved pasta water, and parmesan cheese to the skillet.
Toss the ingredients continuously until a light, creamy sauce forms and coats the pasta evenly.
Remove from heat, drizzle with truffle oil, and garnish with the remaining salt, pepper, and fresh parsley.