Pre-heat oven to 180°C.
Beat butter, castor sugar, brown sugar and vanilla essence until light and creamy.
Add peanut butter and cream well.
Fold in sifted flour, soda and salt to form a stiff dough. Roll into small balls and place on a greased baking tray.
Press biscuits lightly with a fork, first crosswise, then lengthwise.
Bake in pre-heated oven for about 15 minutes or until golden brown. Remove from oven and cool on wire rack.
Recipe reprinted with permission of Source Food.