With smashed pasta & plenty of herbs
I've only ever made this soup with freshly podded peas, but frozen peas work well too.
If I'm using fresh peas, what I like to do to make the soup even more tasty is to boil up the stock with the shells of the peas. You can do this while you're frying the onions. Then you can strain the stock onto your onions and peas when they're ready and fill the pan up again with water to boil your spaghetti while the soup simmers.