Sift the flour with the starch and salt. Rub in the first batch of cold butter with your fingertips, or use short pulses in a food processor, until it looks like coarse wet sand.

Add the sugar with the lemon zest and vanilla, add 9 g of the yolk and work just until combined. Wrap into a disc and chill in the fridge.

Sift the flour with the cocoa, cinnamon and salt. Rub in the second batch of cold butter until it looks like coarse wet sand.

Add the sugar with the orange zest, add 9 g of the yolk and work just until combined. Wrap into a disc and chill in the fridge with the first dough for at least an hour.

Tear both chilled doughs into walnut-sized pieces, stack them alternately in a pile and press with your palm into a disc. Don't knead — kneading will smear the pattern.

Roll the disc out between two sheets of baking paper to 3 mm. The fewer passes with the rolling pin, the bolder the pattern. Don't roll it smooth.

Cut out solid rounds; don't cut a window in the center for this version. The pattern should show across the whole surface.

Put the tray with the cut-outs in the freezer for 10 minutes, or in the fridge for 15 to 30 minutes.

Bake at 170 °C for about 8 to 10 minutes. Go by the light parts of the dough; you can't judge doneness by the dark ones.

Leave on the baking sheet for 3 to 5 minutes, then move to a wire rack and let cool completely.

Warm the apricot jam just enough to loosen it, let it cool to lukewarm and sandwich the cookies with their flat sides together. Don't dust with powdered sugar or coat with chocolate.

Store in a tin, layering with paper between the layers, and let them rest in a cool room for at least three days.