Risi e bisi the classic Venetian dish was traditionally offered to the Doge (do not know which one) on April 25, the feast of Saint Mark. This is not surprising, it is spring in the northern hemisphere and peas are one of the symbols of the season.
It is a public holiday in Venice and all sorts of events take place.
Although Venetians celebrate his feast day they also celebrate Liberation Day (liberation from the Nazis at the end of 2nd World War) and Festa del Bòcolo (is a rose bud) and it is customary for all women, not just lovers, to be presented with a bud. The very old legend concerns the daughter of Doge Orso Partecipazio, who was besotted with a handsome man, but the Doge did not approve and arranged for the object of her desire to fight the Turks on distant shores. The loved one was mortally wounded in battle near a rose bush. There he plucked a rose, tinged with his heroic blood and asked for it to be given to his beloved in Venice.
I grew up in Trieste (not far from Venice and in the same region of Italy) and risi e bisi is a staple, traditional dish.
The traditional way of cooking it does not include prosciutto but prosciutto cotto, what we call ham in Australia. Poor tasting ingredients will give a poor result; use a good quality smoked ham. As an alternative some cooks in Trieste use speck, a common ingredient in the region (it tastes more like pancetta). Some of the older Triestini use lard and only a little oil.
My mother also added a little white wine to the soffritto of onion and the ham, but this also would have been a modern addition. The butter is added last of all for taste. Use parmigiano – parmigiano is the cheese used in the north of Italy, pecorino in the south.
The secret is in using good produce, preferably organic, young and freshly picked peas (for their delicate taste) and a good stock.
My mother made chicken stock. If she had no stock, she used good quality broth cubes- very common in Northern Italian cooking. Use as much as needed.