Drain the salmon and push the excess liquid out of it with a fork through the strainer.
Put it in a large mixing bowl.
Whip the cream cheese with the butter ( if used). ), Add this and the lemon juice and zest to the salmon. Stir the spring onion or chives in and season with salt and pepper.
Now add just enough crème fraîche to be spreadable - it still should hold a shape. Add a few drops of tabasco & Worcestershire sauce and mix well.
Transfer it to a large platter and using clean hands shape it into a skull. Use your fingers create a the nose and the areas for eyes and the mouth. Put two olives in the eye cavity and use almonds or spring onion bits as teeth.
Rest the skull in the fridge to set, for about an hour.