Heat the olive oil in a large frypan over medium-high heat. Coat the chicken in flour, shaking off any excess. Fry chicken in the hot oil until brown on both sides. Remove from the frypan and set aside.
Add the garlic, onion, sun-dried tomatoes and prosciutto to the frypan and reduce the heat to medium. Cook and stir for a few minutes, until garlic is fragrant and prosciutto is cooked. Stir in the sherry, loosening any bits stuck to the bottom of the pan. Simmer until reduced by half. Stir in the chicken stock and cook until reduced by half again.
Whisk together the egg yolks and thickened cream; mix into the frypan. Season with salt and pepper. Return the chicken to the frypan and cook for a few minutes until chicken is coated and sauce is thick. Stir in the Brie cheese until smooth. Remove from the heat and sprinkle with parsley. Serve over rice or angel hair pasta.