Mix the egg and three egg yolk with 25g Tagatesse and a pinch of salt. Keep the three egg whites aside for the meringue. Remove the marrow from the vanilla pod and add it. Also add the soft butter. Mix to a homogeneous mass. Add half of the flour. Knead a little further and add the other half of the flour. Knead further into a dough ball. Wrap the dough in plastic wrap and put it in the refrigerator for 1 hour.