The best thing about potato leek soup, besides its simplicity, is its malleability. You need only four ingredients, plus salt and pepper. Four ingredients! Those four ingredients can be added in different amounts to produce slightly different soups.
Get yourself to the store and purchase anywhere between five and eight leeks. Grab two (large) or three (medium) baking potatoes. Buy a box of chicken (or vegetable, if you're so inclined) broth - you'll need five or so cups, maybe a little more. You probably have butter, but if not, grab that too, preferably unsalted. I'm a fan of unsalted butter for all cooking and baking - for smearing on bread is a different story. For garnish, get a couple slices of bacon from the meat counter and some scallions from the vegetables area too.
Talk about easy: you need a sharp knife, potato peeler, long spoon, soup pot, and cutting board.
Dice your leeks, white part only. Don't fret if you get a little of the greenish part, it won't hurt. I cut mine down the middle to create two half domes, then slice those again down the middle, then slice in half inch increments to make a large dice. Peel your potatoes and slice them thinly. They'll probably turn brownish from oxidation in the open air. The browning is caused by oxidation; if you want your potatoes to stay white, put them under cold water. They'll have to sit for a while anyway, so you might as well. While you've got the cutting board out, slice your scallions, and finally, dice your uncooked bacon.
Melt between one and two tablespoons of butter in a large soup pot, over medium heat. Add your leeks and cook them, stirring them frequently, on medium until they are shiny and fairly translucent. It's very important to watch them and stir them, because a browned leek is a burnt leek is a bad leek is a let's go buy some more leeks and start the soup over. So this leek saute will take about twenty minutes.
When your leeks are soft and shiny, add in about five cups of your chosen broth - for me, the choice will always be chicken. Then add in your potatoes. See, this is incredibly simple. Bring the mixture to a boil, then reduce the heat to a high simmer (not crazy boiling, but some bubbles) and walk away for about a half hour. Actually, only walk away for about twenty minutes, because you want to cook your diced bacon at some point then remove it to a paper towel to drain. When you're done with that task, the potatoes should be soft and beginning to break up. At this point, salt and pepper to your liking. I like a lot of freshly ground pepper in my soup. I throw in a small palmful of salt - it's probably a teaspoon or so. You can always add more later if need be.
Transfer the soup to a blender or food processor (in batches! learn from my mistakes!) and process to your desired consistency. I like mine very smooth, but some people prefer a chunkier soup. You could probably use a potato masher and do this by hand if you wanted more texture.
Top with scallions and bacon and appreciate how something so simple can be so incredibly delicious.
Yum.