Frozen sweet peas are the best option for making this cold pea salad, but you can use canned. I recommend using ones labeled “sweet peas” or “very young small sweet peas.” They’ll be the sweetest and tenderest. Canned peas are softer than frozen peas and may smush a little, so be careful stirring. They’re also not as bright green, so your salad won’t have the same vivid green color.