Heat the olive oil in a large skillet over medium heat. Season the chicken breasts with salt and pepper.
Add the chicken breasts to the skillet and cook for about 6-7 minutes on each side, until golden brown and cooked through. Remove the chicken and set aside on a plate.
In the same skillet, add the diced onion and sauté for about 3-4 minutes until translucent. Add the minced garlic and cook for an additional 1 minute until fragrant.
Pour in the chicken broth and scrape the bottom of the skillet to deglaze and incorporate any browned bits. Allow the broth to simmer for about 3 minutes.
Reduce the heat to low and stir in the heavy cream, pepperoncini peppers, and Italian seasoning. Mix well and let it simmer for another 2-3 minutes for flavors to combine.
Return the chicken breasts to the skillet, submerging them into the creamy sauce. Allow them to warm through for about 2 minutes.
Taste the sauce and adjust seasoning with additional salt and pepper, if necessary.
Garnish with chopped fresh parsley before serving.