In a large sauté pan, melt butter over medium-high heat.
Season chicken with salt and pepper, then add to the pan and brown on all sides, about 8 minutes.
Remove chicken from pan. Add garlic and onion, letting them brown for about 5 minutes.
Add chicken stock and roasted red peppers, reducing the mixture by half.
Turn off heat. Gradually stir in cream and parmesan, whisking continuously.
Return to medium-high heat. Add Italian seasoning, pepperoncinis, and chicken back to the pan.
Let sauce reduce until thickened and chicken reaches an internal temperature of 165°F. Add more stock if needed to adjust consistency.
Serve over your choice of vegetables, pasta, or rice.