In a bowl, beat the butter (taken out of the fridge about 20 minutes before). Add the ricotta, the yoghurt and the seeds from the ½ vanilla pod (cut a slit along the pod and use the tip of a knife to get the seeds out). Mix well, add the flour with a pinch of salt and transfer the mixture onto a pastry board or your table. Knead with your hands until the dough is soft and elastic, then shape it into a ball. Dust the bottom of a bowl with flour, put the ball of dough in it, cover and leave in the fridge for approximately 2 hours. Then take it out, cut off approximately a quarter and use a rolling pin to roll it out until you have a sheet of pastry roughly 3-4 mm thick. Dip the rim of a glass (approx. 8-9 cm in diameter) into some flour and then press it down on the dough to cut out discs. Knead the scraps of dough, roll them out again and cut out more discs.
Now put a heaped teaspoon of jam or Viallella in the centre of each disc – that way you’ll please absolutely everyone! Join edges together by pressing down well with your fingers and then with the prongs of a fork, to seal the biscuits. Continue in the same way until you have finished all the dough. Arrange the biscuits on a baking tray, lined with greaseproof paper, and bake in a preheated oven, at 200 °C, for 15 minutes. Let your half-moons cool down completely, maybe on a cake rack, before serving them.