Cut the potatoes into bite-sized pieces and soak them in water for 5 minutes. Drain the water.

Place the potatoes in a pot with enough water to cover them. Heat on medium until boiling, then cover and simmer on low for 8 minutes. Add green peas and cook for another 2 minutes. Drain and heat on medium to evaporate excess moisture. Let cool.

Thinly slice the onion and rub with salt in a bowl. Let sit for 10 minutes until softened, then squeeze out excess water.