Gradually add in the flour, 100g of the caster sugar, cream of tartar and bicarbonate of soda, until well mixed. In a separate bowl, mix the 25g sugar and spices.
Shape rounded teaspoonfuls of dough into approx 2.5cm balls. Roll the balls in the sugar and spice mixture. Place these on a grease proof liner or cookie tray, about 2.5cm apart.
Bake until edges are lightly browned, about 10 minutes. Remove and allow to cool for 1 minute before transferring to a wire rack to cool.