Preheat oven to 180ºC. Line baking sheets with parchment paper and set aside.

Cream the butter and sugar, until light and fluffy, about 2 minutes.

Add vanilla, lemon juice and lemon zest. Beat until combined.

Add egg yolks, one at a time, beating well after each addition. Reduce speed and gradually add the flour and nuts until fully mixed.

Lightly flour a flat surface and roll out dough to 1/2 cm thickness.

Using a small cookie cutter, cut out cookies and place on prepared baking sheets (we made balls walnut size and shaped them round or like crescents).

Bake about 17 minutes. Let cool 5 minutes on pan, then transfer cooling racks.

When completely cook, spread the underside of half of the cookies with apricot jam (we ommited this).

Make a sandwich with remaining cookies, pressing gently to spread jam to the edges.

Gently toss sandwich cookies in confectioners’ sugar (we ommited this too).