Canned peas

No. They are already cooked, so you can eat them cold in a salad or heat them until steaming for a hot meal.

Drain them, then warm gently in a saucepan with a splash of water for 2–3 minutes, stirring once or twice. Add butter or herbs after heating rather than boiling them hard.

Drain them first; a quick rinse under cold water removes some of the canning liquid and gives them a cleaner taste in salads or pasta. Keep the liquid if you want to add it to a soup or stew.

Refrigerate leftovers promptly in a covered container, rather than leaving them in the opened can, and use them within 3–4 days. Discard them if they smell or look unusual.

Stir them into cottage pie filling, a curry or a tuna pasta salad near the end of cooking so they hold their shape. For a quick side, warm them with butter and chopped mint.

Yes, but add them near the end: canned peas are already soft and need only warming, while frozen peas usually need several minutes of cooking. Drain them first so they do not water down the dish.

Yes, though they are usually softer and less starchy than marrowfat peas, so the result may be looser. Drain them, mash with a little butter and mint, and warm briefly; add no extra liquid unless needed.