In a bowl, cream butter with sugar until very light.
Add well beaten egg, cream and vanilla.
In a separate bowl, sift flour with baking powder; add creamed mixture and blend well.
Roll dough into a log and wrap in aluminum foil.
Chill overnight, or in freezer for 2 hours if rushed for time.
Remove dough from refrigerator, slice very thin and place on greased cookie sheet.
Bake 5-8 minutes at 350.
Variations: For various holidays decorate with colored sugar, beads or icing and or substitute almond or lemon extract for the vanilla to vary the flavor.