Heat the oil in the pan until hot and add the diced onion. Cook over medium heat until it begins to soften, about 5 minutes.
Push the onions to the side of the pan and add the Arborio rice. Cook for a few minutes to coat the rice in the olive oil.
Add a ladle full or two of the stock to the pan and stir and stir and stir. One of the secrets to great risotto is a lot of stirring. You need to take your time and let the rice absorb the liquid before adding more. And keep stirring!
You don’t want to dump all the stock in to the pan and let it absorb like you might with other rice types - just a ladle at a time and lots of stirring.
When the stock is running low, about 2 cups left, add the peas. When you are down to a cup, you can add the salmon and it will reheat in the rice.
Now add the frozen peas. Let this cook for a few more minutes, taste, adjust seasoning with salt and pepper and serve.