Mashed Potatoes

My boyfriend's recipe, created to much acclaim for Christmas dinner:

Ingredients
 - Russet potato
 - 2 Yukon potatoes
 - 1 Red potato
 - 1 Regular sweet potato
 - 1 Garnett sweet potato
 - 1 Onion (we used red)
 - 1 bulb of garlic
 - 2 large spoonfuls of margarine


Directions
 - Chop the sweet potatoes into small (quickly-cooked) pieces, add to pot of water
 - Bring the water to a boil
 - While you are bringing the water to a boil, chop the rest of the potatoes and add them to the pot.
 - Peel and coarsely chop the onion
 - Start to caramelize the onion in a fry pan with olive oil
 - While the onion is starting to caramelize, peel and dice the garlic
 - As soon as you've finished dicing the garlic, add it to the pan with the onions
 - Once the potatoes are cooked, drain them and move them to a bowl
 - Mash the potatoes
 - Stir in the onions, garlic, and margarine