Boil your potatoes in water until cooked well – if you spear one with a fork, it should fall apart.
Drain the water, and leave the potatoes in the strainer as you cook the onion.
Place the olive oil in a stockpot over medium heat, and add the chopped onion. Cook until translucent, about three minutes.
Add the potatoes back in along with the water or broth. Cover, and cook until the potatoes start to break down, about 20 minutes.
Place in a blender, or use an immersion blender, and blend until smooth.
Season with salt and pepper to taste, and garnish as desired. I love shredded cheddar cheese and chives as a garnish, and my boys love crumbled bacon too. Enjoy!