1-1.5tbspmilkdepending on how runny/thick your dough is
Buttercream
100gunsalted butterroom temperature
200gicing sugar
1/2tspvanilla extract
Jam
4tbspraspberry jam
Instructions
For the biscuits: Preheat your oven to 190C/Fan 170C/Gas Mark 5. Line a large baking sheet with baking paper that you have drawn 14 circles on for guidelines. (I draw round a 6cm diameter cookie cutter for mine.)
If using a food processor, blitz the butter, sugar, flour, cornflour and vanilla extract until smooth. You may need to push the mixture down a little. Or add all ingredients to a bowl and beat together by hand.
Then add a little milk at a time until you reach a smooth piping consistency. Spoon the mixture into a piping bag fitted with a star tip, and pipe circles onto the baking paper starting from the outside of the circle and working your way in.
Bake in the oven for 12-15 minutes, until they are firm and pale golden brown.
For the buttercream: While the biscuits are cooling, begin to make the filling by beating the butter in a bowl. Once soft, add in the icing sugar and vanilla extract and beat again until smooth.
To assemble: Spread the jam on the flat side of half of the biscuits once they are completely cool. Then spread or pipe the buttercream onto the flat side of the remaining biscuits. Sandwich the biscuits together, and sprinkle with icing sugar if desired.