Cream together butter, peanut butter, white and brown sugars. Add eggs & vanilla, mix well. Add flour, salt and baking soda. Roll dough into walnut size balls; roll each ball in white sugar. Bake at 350 for 5 minutes or until beginning to look done. Remove from oven and place a chocolate star on each cookie. Put back into oven for 2 more minutes. Cool on pan a few minutes before removing to baking racks.