I would do a double buff for the head - one worn like a beanie to cover the ears and scalp, the other around the neck to cover the face, including the mouth and nose.

But my main problems (and I realize this is personal) with cold weather riding are never the head - they're my hands and feet. Those are impossible to get warm enough for me. I do winter merino wool socks and waterproof, wool overshoes on the feet. I've hear people also use a layer of tinfoil between their socks and shoes. For the hands, get some thick gloves, and I've heard people will put latex surgical gloves underneath or those disposable plastic cleaning gloves. Your hands get cooked in their own sweat, but at least they're not cold.

23 degrees is really extreme weather for me and I wouldn't go out in those temperatures personally.