Prepare the potatoes. Clean 500g of potatoes. If the potatoes are muddy they may need a short soak in cold water to loosen the soil. Remove any earth with a brush or soft scouring pad. Rinse the potatoes under running water. If you have small potatoes, you do not need to cut them. For larger potatoes, cut them into chunks, keeping the skin on.
Cook the potatoes. Put the potatoes into a large saucepan and cover with water. Make sure that no part of the potatoes is above the water. Add a generous pinch of salt to the water. Bring the water to a boil and then gently simmer the potatoes. The cooking time will depend upon the size and type of potatoes but will be about 10 to 20 minutes. Check if the potatoes are cooked by trying to insert a fork into them. If the fork enters easily they are cooked.
Drain the potatoes. Drain the potatoes as soon as they have cooked and let them cool. Whilst the potatoes are cooling, prepare the spring onions.
Prepare and chop the spring onions. Prepare about 3 to 4 spring onions (scallions) by chopping off the root end and, if needed removing the outer leaf layer. Rinse under a cold tap. Finely chop the white end of the spring onions including some of the lighter green part of stems. Reserve some of the greener slices of onion.
Combine the ingredients and season. Put into a large mixing bowl 4 to 5 generous tablespoons of mayonnaise, the chopped spring onions and the cooled potatoes. Mix together well with a large spoon so that all potatoes are well covered by the mayonnaise. Double check the seasoning by tasting a slice of potato together with the mayonnaise dressing. You may find that extra salt and ground pepper is needed.
Sprinkle and serve. You may wish to serve the Spring Onion Potato Salad in a fresh, clean dish. Sprinkle the salad with some of the reserved finely chopped spring onions.