Preheat oven to 180 degrees celsius.
Line two baking trays with baking paper.
Sift the icing sugar into a large bowl.
Add the butter and vanilla essence.
Beat with a stand mixer or hand-held beaters until smooth and creamy.
Sift into the bowl the self raising flour, plain flour and custard powder.
Stir well to combine.
Roll mixture into teaspoonful sized balls and place 5cm apart on the prepared baking trays.
Press the tops of the balls lightly with a fork.
Bake for 10-12 minutes or until just lightly golden.
Leave to cool on the trays for 10 minutes before moving to a wire rack to cool completely.
To make the filling, beat the butter, vanilla essence and lemon juice until smooth and creamy.
Slowly add the sifted icing sugar, beating well in between additions.
When the mixture is completely combined and smooth, add one drop of pink food colouring and beat until the colour is evenly dispersed.
Join two biscuits together with 1tsp of filling.
Store in an airtight container.