For the lemon cream filling:

Cup of Yum
1. Peel the lemon, avoiding the white pith, then juice it until you have 35ml/ 2½ tablespoons.
2. Heat milk with lemon peel until warm (not boiling), then let it infuse for a few minutes. Remove and discard the peel.
3. In a large saucepan, whisk egg yolks, lemon juice, and sugar until creamy. Mix in sifted flour, then slowly whisk in warm milk.
4. Return to the saucepan and cook over low heat, stirring until thick (about 5 minutes). Transfer to a shallow dish, cover with plastic wrap (pressing it directly onto the surface), and cool completely.

For the cookie dough:

1. In a food processor, blend powdered sugar, extra-virgin olive oil, whole egg, egg yolk, lemon zest, and a pinch of sea salt on low speed. Gradually add ⅔ of the flour and baking powder until the dough starts to come together.
2. Transfer the dough to a work surface, gradually adding the remaining flour while kneading until smooth (you may need slightly less than 280 grams/9.8 oz). Use immediately or shape into a thick disc, wrap in cling film, and chill for 30 minutes for easier rolling.

For the cookies:

1. Preheat oven to 180°F (200°C). Arrange the baking tray into the middle shelf. Line a baking sheet with parchment paper.
2. Divide the dough in half and sprinkle each with the remaining 1 tablespoon of flour. Roll each half between two sheets of parchment paper to a ⅛-inch thickness.
3. Using a 2-inch round cutter, cut out circles from both halves of the dough. Add 1 teaspoon chilled lemon pastry cream in the center, and top with another circle. Pinch the edges to seal, brushing edges with a little water if necessary. Place cookies the lined sheet pan, spacing them at least 2 inches apart.
4. Bake for about 10-12 minutes, until the cookies are golden and the tops look dry. Cool on the sheet pan for 2 minutes, then transfer to wire racks to cool completely. Dust with optional powdered sugar and serve.