Place the soft butter and icing sugar into the bowl of an electric mixer and combine.
Add the flour to the mixture along with the vanilla. Mix, on a medium speed, until it is soft and pale. This will take about 10 minutes, as you need to make sure the mixture is soft and easy to pipe.
Line a baking tray with parchment paper.
Place the mix into a piping bag fitted with a star nozzle and pipe the mixture into the desired shape; either round or finger shaped. They will spread a little in the oven so allow some room for this on the tray. If you wish to sandwich them together allow 2 per portion.
Bake in the pre heated oven for 10 – 15 minutes or until golden brown. The biscuits are very delicate when warm so allow to cool on the baking tray before transferring them to a cooling rack.
Meanwhile make the buttercream. Mix the softened butter, icing sugar and vanilla together and beat until soft and light. This will keep really well in the fridge for 7 days, so if you have any leftover put it away for another day.
Either dip the biscuits in melted chocolate or pipe buttercream onto the flat side of one of the biscuits spoon a dollop of jam on the top and place another biscuit on top. Dust with icing sugar and serve.