Add the butter to a heated, easy bottomed pot. Sauce the onion till golden. Add the peas and sea salt to taste and saute for 2 minutes stirring frequently.
Add 3½ cups of broth and cook at a rapid simmer for 10 minutes. Add the rice and parsley and stir. Cover the pot and cook at a rapid simmer until the rice is tender but still firm, about 15 minutes stirring occasionally. The rice and peas should still be a bit soupy. Add a bit more broth if necessary.
Switch off the heat add the grated parmigiano and stir well into the rice and peas. Add a grind of black pepper and sea salt if necessary and stir well.
Put the risi e bisi in individual bowls or a large serving bowl, top with a sprinkle of grated parmesan.
