Bring a large pot of salted water to a boil and cook the chickpea tagliatelle according to package directions until al dente, reserving 2 tablespoons of pasta water.
Season the chicken breast with half of the salt and pepper, then grill or pan-sear over medium-high heat until cooked through, about 5-6 minutes per side.
While the chicken rests, melt the ghee in a large skillet over medium heat and add the sliced cremini mushrooms.
Sauté the mushrooms until they release their moisture and turn golden brown, then add the minced garlic and sauté for another 60 seconds until fragrant.
Slice the rested chicken into thin strips.
Add the cooked pasta, sliced chicken, and reserved pasta water to the skillet with the mushrooms, tossing gently to combine.
Remove the skillet from the heat and drizzle with the truffle oil, then sprinkle with the remaining salt, pepper, and grated parmesan cheese.
Garnish with freshly chopped parsley and serve immediately while hot.