Braise the onions with the butter in a wide pot with a thick bottom on moderate heat. After 5 min, add the rice, stir and season with salt and black pepper.
After 2 min. of stirring, pour in 2 cups of chicken broth and leave it to simmer until the rice swells. After about 6 min. pour in another 2 cups of chicken broth and stir periodically for another 6 min. - the rice needs to boil but remain slightly hard.
Separately, heat the olive oil in a pan and add the pancetta. Braise about 2 min. but be careful not to have it brown. Add the chopped green onions to the pan and stir for 1 min, then add the garlic, salvia and peas.
Sprinkle generously with salt and black pepper to taste and pour in another 1/2 cup broth. Leave the dish to simmer until the peas (small ones are best) are ready. Finally, add the leaves of baby spinach and cook for about another 1 min.
Combine the vegetable part with the rice and stir carefully. Pour in the remainder of the broth so that the dish ends up juicy and not dry. Add some more spices to taste and mix with the parsley, lemon zest. Sprinkle with parmesan and serve Risi e Bisi right away.