Add the ice-cream, yoghurt, and milk to a blender and blend until smooth.
Pour into glasses.
Whip the cream until soft peaks form and then add the icing sugar and whip until stiff. Spoon into a piping bag fitted with a star nozzle and pipe a swirl of whipped cream onto each milkshake.
To serve:
Sprinkle over some cinnamon and decorate with a Biscoff biscuit.
