I'm half Scottish, so leek and potato soup is a no-brainer comfort food for me.
I love soups in general—they're easy to make, inexpensive, and a great way for me to consume my veggies. Plus they're easy to freeze, which makes them convenient. All I have to do is stick a frozen container of soup in my fridge the night before, and I have an almost-instant meal the next day.
Another thing I love about leeks is that they add a really subtle, distinctive flavour to soups that onions can't match. Leeks are always my first choice when I need an allium-family base for any soup.
To make the soup, I first wash the leeks (today I used the whole bunch of three). Leeks need special cleaning, since they're often grown in sandy soil and need to be thoroughly rinsed.
I cut off the tough ends of the leaves (anything that's dark green), then cut off the root end. Next I make a slice down the length of the leek, without going all the way through.
Under running water, separate the individual layers without actually taking them apart, and make sure that you rinse away any visible sand or dirt.
I puree most of my soups, so I don't worry about how nicely chopped everything is. Just make the pieces small enough so that they don't take forever to cook.
Heat some olive oil (I use about a quarter of a cup) in a large soup pot. Add the leeks, stir to cover them with the oil, and then turn the heat down to low and let them simmer for 5-10 minutes, until they soften and start to wilt.
Then add four chopped potatoes (you can remove the skins first if you want, but I often don't bother. I like the rustic texture of bits of skin in my soup. Today I used new potatoes, and left them unpeeled).
Fill the pot with enough water to just cover everything, and put the pot on the stove to simmer until the potatoes are cooked.
Instead of plain water, you can also add any vegetable stock that you've got. I usually save the cooking water whenever I cook vegetables, and freeze it in jars to use in soup-making. Today I had a bit of carrot water to add to the soup. I don't like using commercial stock powders since I find the taste too harsh, but do whatever's convenient for you.
After the potatoes are soft, take the pot off the stove and puree the soup in small batches in a blender or food processor. I'm a pretty hearty risk-taker and puree everything while it's still steaming hot, but you may wish to let the soup cool first before pureeing. When pureeing soup in the blender, I make sure to add extra water to each batch if needed—enough to cover all the solid food chunks thrown in the blender jar.
After the soup is pureed, add salt to taste. This time I tried out some of the smoked salt I re-bottled yesterday, and it was an amazing addition to the soup, giving it a dense, rich flavour.
When my soup is done, I put it in individual wide-mouthed Mason jars and freeze them. (Make sure you cool the filled jars overnight in the fridge, before putting them in the freezer. And be sure to leave enough space in the jar for the soup to expand a little as it freezes.)
This soup also makes a great base for a number of other dishes. Add some cooked vegetables and you have a great vegetable soup. A favorite variation of mine is adding chopped fresh tomato.
Add a LOT of cooked veggies, and you have a stew.
The soup can also can be used as a white sauce over veggies, or as a hot dip for a hearty, rustic bread.