Cut the chicken into thin strips and season with sea salt and ground pepper on all sides.

In a large heavy skillet, melt the butter over medium-high heat. Add the chicken strips in a single layer and cook until browned on all sides, about 8 minutes. Work in batches if needed. The chicken does not need to be fully cooked through at this stage. Remove from skillet and set aside.

Add the diced onion and garlic to the same skillet and saute over medium-high heat until fragrant and golden, about 5 minutes.

Pour in the chicken stock and roasted red peppers. Let the mixture reduce by half, about 5 minutes, to concentrate the flavor.

Turn the heat off completely. Slowly stir in the heavy cream and shredded Parmesan cheese, whisking vigorously to create a smooth, creamy sauce with no lumps.

Return the heat to medium-high. Stir in the Italian seasoning and drained pepperoncini peppers. Taste and adjust salt if needed.

Add the browned chicken back to the pan and simmer until the chicken reaches an internal temperature of 165 degrees F and the sauce has thickened to a creamy, coating consistency. If the sauce becomes too thick, add more chicken stock one tablespoon at a time.

Serve hot over rice, pasta, or roasted vegetables. Garnish with extra shredded Parmesan and fresh parsley if desired.