Start by seasoning the chicken breasts generously with salt and pepper on both sides.
In a large skillet, heat the olive oil over medium-high heat. Once hot, add the chicken breasts and sear for about 5-6 minutes per side until golden brown and cooked through. Remove from the skillet and set aside.
In the same skillet, add the sliced onion and sauté for about 3-4 minutes until translucent. Add the minced garlic and sauté for an additional minute until fragrant.
Pour in the chicken broth, scraping the bottom of the skillet to deglaze and pick up any flavorful bits.
Stir in the pepperoncini slices and Italian seasoning, allowing the mixture to simmer for about 2-3 minutes.
Reduce the heat to low and pour in the heavy cream, stirring to combine. If using, add in the grated Parmesan cheese at this stage for a richer flavor.
Return the seared chicken breasts to the skillet, ensuring they are coated with the creamy sauce. Let them simmer together for an additional 5 minutes to heat through and combine flavors.
Adjust seasoning with additional salt and pepper if needed.
Remove from heat and garnish with chopped fresh parsley before serving.
Notes
Serve on a bed of mashed potatoes or pasta for a complete meal.