Blanch the julienned vegetables in water until desired doneness. Season chicken with salt and pepper. Heat clarified butter in a skillet and saute chicken until golden brown on both sides. Remove and set aside. Add onion and mushrooms to skillet and saute until onion is golden brown. Add riesling and vegetables. Reduce until all liquid has evaporated. Remove vegetable mixture and set aside. Add half and half and chicken stock to the skillet. Reduce to a sauce consistency. Blend the sauce, add the chicken and vegetables. Season with salt and pepper. Reheat for a moment and swirl in the butter. Serve.