Combine 150 grams flour, 75 grams butter, 40 grams sugar, 1 egg yolk, and a splash of lemon juice until the dough comes together. Form a disc, wrap in plastic, and refrigerate for 30 minutes.
Preheat oven to 160 °C (320 °F). Roll out dough between parchment paper, cut into round cookies, and place on a baking sheet.
Bake for 10 minutes with top and bottom heat until the edges are lightly golden. Cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.
Once completely cool, brush each cookie with jam, cover the top with marzipan, cover the sides with chocolate icing, and top with a walnut half.