Boil a pot of salted water and cook the red lentil tagliatelle according to package directions until al dente.
While the pasta cooks, heat the olive oil in a large skillet over medium-high heat.
Add the diced chicken breast to the skillet, seasoning with half of the sea salt and black pepper, and cook until golden and cooked through.
Remove the cooked chicken from the pan and set it aside on a plate.
In the same skillet, add the sliced cremini mushrooms and minced garlic, sautéing until the mushrooms are tender and deeply browned.
Drain the pasta, reserving 2 tablespoons of the starchy pasta water.
Return the chicken to the skillet with the mushrooms, then add the cooked tagliatelle and the reserved pasta water.
Drizzle the truffle oil over the mixture and toss everything together until the pasta is evenly coated and the sauce is glossy.
Serve immediately topped with the grated parmesan cheese, chopped fresh parsley, and the remaining salt and pepper.