Alessio began by pouring about a half cup of cream into a jar, adding the saffron pistils, covering the jar, giving it a good shake to sink the pistils, and putting it in the fridge.
He next made the sponge cake -- a Genovese -- by beating the eggs and sugar over a double boiler, beating constantly until the mixture reached a temperature of 50 C (about 120 F) over a double boiler.
He then cooled the mixture by putting the top half of the double boiler in a pot of cold water, whipping constantly, and then added the flour in one fell swoop and continued to whisk the mixture for several minutes, until it looked right. At this point he gently folded in the butter, and turned the batter out into a 10-inch (25 cm) ring pan lined with oven parchment, and buttered and floured.
He baked the cake in a preheated 380 F (190 C) oven for 20 minutes, and turned it out on a rack to cool. Because the saffron had to soak, everything else happened the next day.