Season the chicken breasts all over with a generous sprinkle of salt and freshly ground black pepper, ensuring they are well-coated.
In a large skillet, heat the olive oil over medium-high heat. Once the oil is shimmering, carefully place the chicken breasts in the skillet. Sear for approximately 5-6 minutes on each side, or until the chicken is golden brown and reaches an internal temperature of 165°F (75°C). Once cooked through, transfer the chicken to a plate and set it aside.
In the same skillet, add the thinly sliced onion. Sauté for about 3-4 minutes, stirring frequently, until the onions become translucent and slightly softened. Add the minced garlic and continue to sauté for an additional minute, or until the garlic is fragrant but not burned.
Pour the chicken broth into the skillet, using a wooden spoon to scrape the bottom to deglaze the pan. This will release any flavorful bits stuck to the skillet.
Stir in the sliced pepperoncini peppers along with the Italian seasoning. Allow the mixture to simmer for about 2-3 minutes, letting the flavors meld together.
Lower the heat to a gentle simmer and pour in the heavy cream. Stir thoroughly to combine the cream with the other ingredients. If desired, stir in the grated Parmesan cheese at this point to add a rich, cheesy flavor.
Return the seared chicken breasts back into the skillet, ensuring they are well-coated in the creamy sauce. Allow the chicken to simmer in the sauce for an additional 5 minutes, heating through and allowing the flavors to meld beautifully.
Taste the sauce and adjust the seasoning with additional salt and pepper as necessary.
Remove the skillet from heat and sprinkle with chopped fresh parsley for a vibrant touch before serving.
Notes
For an impressive presentation, serve with mashed potatoes or pasta.