Place the plain flour and cornflour into the Thermomix bowl and sift for 20 seconds, Speed 4. Set aside in a seperate bowl.
Place the butter, vanilla and icing sugar into the Thermomix bowl and mix for 40 seconds, Speed 3. Scrape down the sides of the bowl and repeat.
Add the reserved flour/cornflour mixture and mix for 20 seconds, Speed 3. Scrape down the sides of the bowl and mix for a further 10 seconds.Note: if the mixture is too sticky, add a little more flour and mix through.
Roll teaspoonfuls of mixture into balls.Place onto the prepared trays, about 3cm apart.Use a fork dusted with cornflour to gently flatten.
Bake for 15 minutes or until lightly golden and cooked through.
Allow to cool on the tray for 10 minutes before transferring to a wire rack to cool completely.
To make the filling, place the butter and icing sugar into a clean and dry Thermomix bowl. Mix for 30 seconds, Speed 4.
Add the passionfruit pulp and mix for 10 seconds, REVERSE, Speed 3.
Spread a small amount of filling onto the flat side of one of the biscuits. Sandwich with a similar sized biscuit.
Repeat until all of the biscuits have been used.
Notes
RECIPE NOTES & TIPS
I recommend using icing sugar mixture for the biscuits but pure icing sugar for the icing (pure icing sugar sets firmer).
Salted or unsalted butter can be used in the biscuits and the icing.
Substitute the passionfruit pulp for lemon juice and finely grated lemon zest if you prefer.
If using tinned passionfruit pulp, try to use as many pips as possible and don't overload the liquid as it will make your icing too runny.
Don't overcook the biscuits - they should be soft, crumbly and melt-in-your-mouth.
Ensure the biscuits have completely cool before adding the icing (otherwise it will melt!)
Sandwich similar-sized biscuits together with the icing.
Store in an airtight container at room temperature for up to 1 week.