For this one, I was trying to replicate the very famous cake from Biscottificio Mattei in Prato (the most famous biscotti or cantuccini for the Italians) and so I came up with these numbers
130 g yolks (just because I've always extra yolks)
70 g egg whites (you can adjust this proportion a bit but use at least 80 g yolks)
150 g sugar (divided, keep some for the whites)
150 g butter (softened)
vanilla/lemon oil
170 g cake flour
pinch of salt
bakers ammonia (the tip of a knife, but most recipes use a very small amount of baking powder and many others included the Artusi, none)
almond and optional pine nuts for the topping
Whip the yolks with the sugar, add little by little the soft and cold butter, then alternate the flour with the meringue without deflating it