Bring a large pot of heavily salted water to a rolling boil. Drop in the whole wheat fettuccine and cook according to package directions until al dente (about 9-10 minutes). Just before draining, carefully scoop out and save 1/2 cup of the starchy pasta cooking water. Drain the rest of the pasta and set aside.

Pat the chicken breast pieces dry with a paper towel. Toss them in a bowl with the extra virgin olive oil, garlic powder, salt, and black pepper. Heat a large, deep skillet over medium-high heat. Add the chicken in a single layer (do not overcrowd) and sear for 5-6 minutes, turning once, until a golden-brown crust forms and it is fully cooked through. Transfer to a plate.

Lower the skillet heat to medium. Add the butter directly to the pan pan juices. Toss in the sliced cremini mushrooms and let them cook undisturbed for 4-5 minutes until they release their water and become deeply caramelized. Stir in the minced fresh garlic and cook for 1 minute until highly fragrant.

Pour the low-sodium chicken stock into the skillet to deglaze. Use a wooden spoon to vigorously scrape up all the delicious browned bits stuck to the bottom. Let it simmer for 1-2 minutes until reduced by half.

Reduce the heat to medium-low. Pour in the heavy cream and bring to a very gentle simmer. Let it cook for 3-4 minutes to thicken slightly. Whisk in the freshly grated Parmesan cheese until completely melted and smooth.

Add the cooked chicken (along with any resting juices) and the drained fettuccine back into the skillet. Toss everything together well with kitchen tongs. If the sauce feels too thick, splash in a few tablespoons of your reserved starchy pasta water to make it ultra-glossy and smooth.

Turn off the heat. Top with freshly chopped flat-leaf parsley, extra cracked black pepper, and an optional extra sprinkle of Parmesan. Serve hot.