Stir together the butter, sugar, egg yolk,
vanilla and zest from 1 lemon using a
wooden spoon. Stir in the flour – you
might need to get your hands in at the end.
Tip onto a floured surface, bring together
into a smooth dough, then roll out, half
at a time, and stamp out 5-6cm rounds.
Keep re-rolling trimmings, you should get
about 40 biscuits. Arrange on trays lined
with baking parchment, cover with cling
film and chill for 30 mins.
Heat oven to 200C/180C fan/gas 6.
Bake the biscuits for 8-12 mins until pale
golden, then cool. Once cool, spread half
the biscuits with a little lemon curd and
top with a second biscuit. Arrange the
biscuits on wire racks over trays. Mix
enough lemon juice into the icing sugar
to give a runny consistency, then drizzle
over the biscuits. Scatter over a bit more
lemon zest and leave to set.