Rub the chicken with olive oil and season liberally with 2 tablespoons cajun seasoning on both sides.
In a large skillet over medium-high, add olive oil and cook chicken undisturbed for ~3 minutes until it has a good sear. Flip once, turn heat to simmer and add 1/2 cup chicken stock. Cover with a lid and let simmer for 6 minute or until internal temp reaches 165 degrees. Then remove and tent with foil.
Drain excess liquid. Cook sausage until cooked through. Set aside, reserving 1 tablespoon of oil in the pan.
Over medium low, add butter, garlic and pepperoncini, sauté over medium until fragrant, about 1 minute.
Whisk in cream, 1 tablespoon cajun seasoning, pepperoncini juice. Bring cream sauce to a simmer, while cooking the penne to package instructions. Add parmesan into the , penne, and sausage into cream sauce. Toss to coat, adding reserved pasta water if needed. Top with sliced chicken and serve.