Use your preferred type of potato. I used 'Destroyer' potatoes, but any kind works. For the onion, I used a sweet onion, but use your favorite. Thinly slice the onion.

Finely chop the sliced onion.

Wrap the potato loosely in plastic wrap and microwave for 3 minutes. To prevent bursting, poke a few holes in the potato with a toothpick first.

While the potato is still hot, press down on it with the back of a fork or the side of a knife over the plastic wrap to split the skin, making it easy to peel.

Peel the potato and place it in a bowl.

While the potato is still hot, add the onion, mayonnaise, salt, and pepper. Mix well. You can mash the potato smooth or leave it chunky, as you prefer.

Boil the edamame and drain. You can also use chilled or frozen edamame.

Add the edamame to the bowl.

Mix everything together. For extra flavor, add mustard or vinegar if you like.

Done!