Sift the flour,
cornstarch, and salt into a medium bowl. Beat the
butter and granulated sugar in a large bowl with an
electric mixer at high speed until creamy.
Add the
lemon juice and egg yolk, beating until just
blended. Mix in the dry ingredients to make a
soft, sticky dough.
Cover with plastic wrap and
refrigerate for 30 minutes. Preheat the oven to
350°F/180°C/gas 4. Line three cookie sheets with
parchment paper.
Form the dough into balls the
size of walnuts and place 1 inch (2.5 cm) apart on
the prepared cookie sheets.
Make a slight hollow in
each center and fill with a small amount of Lemon
Curd.
Bake, one batch at a time, for 20-25 minutes,
or until just golden. Transfer to racks to cool. Dust with the confectioners' sugar.