Gather all ingredients.
Cut chicken breasts into cubes; season both sides with salt and black pepper.
Heat olive oil in a large skillet over medium heat. Place chicken in skillet and cook until lightly browned and no longer pink in the center, about 6 minutes. An instant-read thermometer inserted into the center should read 165 degrees F (74 degrees C). Transfer cooked chicken to a plate and set aside.
Add onion to the skillet; cook 2 minutes. Add garlic; cook until fragrant, about 1 minute. Add broth, oregano, and crushed red pepper. Simmer until reduced by half, about 2 minutes.
Stir in cream, Parmesan, and pepperoncini brine. Bring to a simmer and cook until slightly thickened, about 5 minutes.
Return chicken to skillet and toss to coat. Add sliced pepperoncini.
Serve garnished with parsley if desired.
