It is a sweet prepared in the pastry shops of Pavia on December 9th, the day dedicated to Saint Siro, the first bishop and patron saint of the city of Pavia. The Pane di San Siro is a delicious cocoa sponge cake, slightly soaked in rum, filled with hazelnut buttercream and covered with a chocolate glaze featuring the inscription "San Siro." The shape is round, and the weight ranges from 800 grams to 1 kg. It has an intense chocolate flavor and a delicate rum aroma.

According to tradition, it was Saint Siro who brought to Nazareth the baskets containing the five loaves of bread and the five fish of the miracle of the multiplication. The Saint is closely linked to the history of Pavia because, after the death of Jesus, his teacher, he was sent by Ermagora to Pavia to spread the word of the Messiah alongside the Levite Invenzio. The legend tells that upon their arrival, even before hearing the sermon, the people converted upon hearing of the miracles that the blessed Father Siro had performed during the journey and ran to meet him joyfully.

The presence of the Saint is thus connected to the city of Pavia and its culinary tradition, with the production of Pane di San Siro on December 9th, the day dedicated to Saint Siro, the first bishop and patron saint of the city.