Chop potatoes into bite sizes pieces and boil in salted water
Hard Boil eggs (seperately unless youre an absolute menace) 10 mins in boiling water
Chop onion into little bits
Cool eggs, peel and lightly mash
Drain potatoes and shake them about to make the edges soft
Put potatoes and eggs in a big bowl, add mayonaise onion and mustard to your liking and salt if it needs
Eat!