Cream together butter and sugar.
Add sifted dry ingredients. Mix to shortbread consistency. Stir in vanilla essence.
Divide dough in two. Add pecan nuts to one half, almonds to the other.
Roll each portion into walnut-sized balls, place on baking tray. Bake at 150ºC for 30 minutes.
When cool roll in icing sugar allow to cool on wire cooling rack.