Heat the oven to 175C
Being wonderfully lazy put all the biscuit ingredients into a food processor and mix until they combine. Once combined place about 2cm diameter balls on baking parchment leaving a reasonable gap between each ball. Now get a cup of cold water and a folk, wet the folk and then press down gently on the balls to flatten slightly.
Place in the oven and cook for about 12 - 15 minutes
Once cooked allow to cool on the parchment for 10 minutes before transferring to a cooling rack.
Make the filling; in a small bowl soften the butter to its easy to work with and then add the vanilla extract and icing sugar. Work with a fork until the filling becomes smooth.
Make the biscuit; once the biscuit is cold, you dont want to melt the butter turn over half the biscuits and equally distribute the filling over the up turned biscuits. Now put the tops on, easiest way of doing this to avoid the biscuit crumbling i to place the top biscuit on and then gently twist back and forward applying very little downward pressure.