Place the softened butter, icing sugar, and vanilla into a large mixing bowl

Whisk everything together until well combined, this will take around 1 minute with an electric whisk. Scrape the bowl with a spatula halfway through whisking to ensure everything is getting combined evenly

To make the freeze dried strawberry powder, place the freeze dried strawberries and cornflour (cornflour for UK readers and corn starch for US readers) into a blender jug

Blitz into a fine powder, the cornflour helps to prevent sticking and clumping of the berries

Then, sift the flour, salt, and the berry cornflour mixture into the whipped butter and icing sugar

Whisk once again on a low speed to incorporate the dry ingredients, this won't take long at all. Once the flour and berry powder look well incorporated, stop whisking. Over whisking can create tough and dense biscuits rather than light and tender

Finish the dough by lightly beating with a spatula, this will help to ensure all the dry ingredients are mixed in. It will also help to remove any pockets of air. This should be quite a soft dough as it needs to be piped

Transfer the dough into a piping bag fitted with a 1M nozzle

Push the mixture to the end of the bag and press out any air pockets

Pipe just under 2" swirls on to a baking tray lined with baking paper. Allow 1" of space between each swirl. It's worth drawing out 2" guidelines on the underside of the paper to use as a referenceNote: if the dough feels slightly firm and is difficult to pipe smoothly, hold the filled piping bag in your hand for 1-2 minutes. Your body heat will help to soften the fat ever so slightly to make it more pipeable

Place the tray uncovered into the fridge for 30 minutes/up to 45 minutes. At the same time start pre-heating the oven to 160'C (fan)/180'C (conventional) - 320'F (fan)/355'F (conventional)

Bake the biscuits for 10 minutes, we don't want to develop any browning or colour on these in order to preserve the pink. Allow to cool for around 5 minutes before carefully transferring to a wire rack to cool completely. They will firm up as they cool

Place the softened butter, icing sugar, salt, and vanilla into a mixing bowl

Whisk everything together on a low speed, and gradually increase the speed to medium once all of the icing sugar has been incorporated. This will take about 4-5 minutes of whisking in total

You should be left with a light, pale, and fluffy buttercream. It will be slightly softer than a traditional American buttercream as we're using a lot less sugar here. If it feels too soft, pop it into the fridge for 10 minutes

Place the buttercream into a piping bag fitted with any small round or star shaped nozzle. Pipe a ring of buttercream around the outside of the cooled strawberry biscuit but leaving a slight border, as well as a small space in the centre (for the jam). Alternatively you can spoon a small amount of buttercream if you do not wish to use a piping bag here

Add a small dollop of jam right into the centre. I used strawberry conserve which was more chunky with very small pieces of strawberries running through it (highly recommend!)

Place another biscuit on top and very gently press together

Finish the Strawberry Viennese Whirls with a light dusting of icing sugar for that classic finish

They can be enjoyed right away, although I do like to place them back into the fridge for 10-15 minutes for the jam and buttercream to firm up slightly