For the dough, quickly knead 300 g flour, sugar, 1 pinch of salt, lemon zest, 2 tablespoons of cold water and butter in pieces to form a smooth dough. Shape into a flat brick. Cover and chill for about 1 hour.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Line two baking trays with baking paper. Roll out the dough on a little flour to a thickness of approx. 1⁄2 cm and cut out approx. 25 rectangles (each approx. 5 x 7 cm), kneading the dough remains again, roll out and cut out.
Put them on the trays. Bake in a hot oven for about 15 minutes. Take out, let cool down.
For the decoration, knead the fondant and roll out approx. 2 mm thin on a work surface lightly dusted with icing sugar. Cut out approx. 25 rectangles (5 x 7 cm each). Knead the rest of the fondant and colour it red with red food colouring.
Roll out in the same way and cut out mini hearts (approx. 1 cm Ø each). Warm the jelly slightly and spread on the cookies. Place white fondant rectangles on top. Brush the hearts with a little water and stick them as a stamp on the biscuit post.
Put some food colouring about 1 cm wide on the fine prongs of a pastry sheet (alternatively a fork). Spread it in a wave shape on the biscuit post.