In a large bowl, cream together the butter and white sugar until light and fluffy. Beat in the
egg, then stir in the vanilla. Combine the flour and salt; stir into the sugar mixture, add
sultanas into the dough (optional). Cover and chill for at least one hour. Chill cookie sheets.
Preheat oven to 400ºF / 200ºC. Press dough out onto ungreased,chilled cookie sheets.
Bake for 8 to 10 minutes in the preheated oven, or until lightly golden at the edges. Remove
from cookie sheets to cool on wire racks.