Leek and Potato Soup

This Classic Is Wonderful as a First Course, Hearty Enough for a Main

Leek and Potato Soup is flavorful and easy to make, and everyone who tastes it enjoys it.  It’s also versatile.  You can prepare a simple vegan version, or fancy it up with cream or stock for vegetarian and carnivorous variations.

So why has it been so long since you’ve made it? 

It’s probably that leek thing.  Leeks often carry some dirt, so they take a few minutes to clean.  Although every supermarket stocks them, they’re usually expensive compared to onions.  And onions are almost the same thing, right?

Well, no.  Similar, but leeks have more depth of flavor, and are a bit less in-your-face than onions.  As you’ll discover when you taste this soup.  Once you do, you’ll be wondering where leeks have been all your life.

Recipe:  Leek and Potato Soup

All you really need for this soup are leeks, potatoes, salt and pepper, and water.  And maybe an optional garnish of parsley or chives.  That’s it.

You can gussy it up with stock, milk, cream, sour cream, or butter.  If you add cream and chill it, you’ll have vichyssoise, which used to be a favorite at snooty restaurants.  I’ll discuss variations in the Notes. 

At heart, though this is a simple peasant dish.  For them, it was dinner, served with some bread.  For us?  Well, maybe also add a salad and a nice bottle of wine.

Although I provide specific ingredient quantities, precise measurements really aren’t necessary.  Basically, you want more or less equal quantities of cleaned and cut up leeks and potatoes.  Then add about as much liquid (maybe a bit less) as you have leeks and potatoes.

Julia Child offers several versions of Leek and Potato Soup in her various cookbooks, but I think her best is in The Way to Cook. My recipe is very slightly adapted from hers, and serves 6 to 8.

This dish requires about 10 to 15 minutes prep time, then 30 minutes or so to cook the soup. Leftovers can be stored in the refrigerator for a few days, and they also freeze well.

Ingredients

• ~4 cups sliced leeks, using the white part and just a bit of the tender light green (usually about 3 medium-sized leeks; see Notes)
• ~4 cups scrubbed and diced potatoes (skinned or not; I prefer Yukon Golds)
• 7 - 8 cups water (use the lesser amount if you plan to enrich later with milk or cream; see Notes)
• salt to taste (at least 1½ teaspoons; I usually use 2½ or 3 teaspoons)
• black pepper for seasoning (to taste)
• 2 tablespoons minced parsley or chives for garnish (optional)

Procedure

1. Clean the leeks.  Leeks can be a bit dirty, so proper washing is mandatory.  To clean them, first remove the first layer if it is wilted.  Cut off the tops right at the point where the leek turns from light green to a deeper shade of green.  Slice off the tip of the root, being careful to keep leaves attached.  Slice the leek in half lengthwise, keeping just a bit of the root end intact so the leaves don’t separate.  (If your leeks are particularly fat, cut them again lengthwise — at which point you’ll have cut them into fourths.)  Now wash under cold running water, separating each leaf so the stream of water can rinse away any dirt.
2. Once your leeks are clean, cut them into thin slices (about 1/8 inch thick).
3. Scrub the potatoes (peeling them or not as you choose), and either cut them into ½ inch dice, or else cut them in half and cut into slices no more than ¼ inch thick.
4. Add sliced leeks and potatoes to a 4-quart pot, and add 7 to 8 cups of water.  Bring to a simmer, and salt to taste.
5. Simmer slowly for 30 minutes, until leeks and potatoes are tender.  (The soup will be done, although you can simmer it on low for up to another half hour if you’re not ready to serve.)  Before serving, taste and add salt and pepper to taste.  If you want a more homogenized soup, you can use a stick blender to puree it.  Or you can cool the soup, puree in a food processor, and then reheat to serve.  (See Notes for more about pureeing.)
6. If you want to make the soup ahead of time and serve later, prepare through Step 5.  Cool the soup and then refrigerate it in an airtight container until you’re ready to serve.  At that time, you can heat the soup in about 5 minutes.
7. A garnish of minced parsley or chives is both attractive and tasty.

Notes

• Although leeks and onions belong to the same botanical family, mature leeks look more like big scallions than onions.  They also have a milder flavor than onions, and one that’s a bit more complex. 
• The edible part of the leek is the white base (starting just above the roots) extending up through the light green parts.  The dark green parts are technically edible, but they have an extremely tough texture.  You might want to use them if you’re making soup stock, however — they’ll add great flavor, and you can discard them when the stock is finished.
• Leeks vary in size from thin to quite fat, so when you're buying them you have to guesstimate how many you need. 
• BTW, the leek is a national symbol of Wales.
• I like to keep this soup relatively chunky, so I give it only a few whirls with my stick blender (in Step 5) to puree it just a little.  This turns the soup pleasantly cloudy, but you still will have some good-sized pieces of potato.  Puree longer with your stick blender if you like a more homogenized texture.
• If you use a stick blender to puree the soup in Step 5, use one with a metal shaft.  Plastics shafts can crack in hot liquid (ask me how I know).
• If you want a totally smooth soup (which you may for some of the variations we’ll discuss below), it’s easier to cool the soup and then puree in the food processor, blender, or food mill.  Pureeing hot soup can be problematic.  Steam forms, so in a blender, for example, you can blow the lid off and splash the contents all over your kitchen (again, ask me how I know).
• I sometimes like to garnish each bowl of soup with a dollop of sour cream.
• If you want a richer soup than this water-based version, you can substitute chicken, turkey, or vegetable stock.  Beef stock would be too strong, IMO.
• If you want to enrich your soup even more, you can add milk, cream, or sour cream.  Right before serving, add about ¾ cup to the soup and simmer for a minute or two to incorporate the flavor.
• If you’re using milk, use whole milk — skim or 2% just doesn’t add that much flavor.
• Instead of cream, milk, or sour cream, you can also enrich the soup with butter.  Right before serving, remove the soup from the heat and, by tablespoons, beat in 2 or 3 tablespoons of butter.
• For vichyssoise, make the basic soup using 6 or 7 cups of chicken stock.  Add 1 cup of cream when the soup is finished, and beat in.  Adjust seasoning (over-season a bit because seasonings lose some of their punch in cold food).  Chill the soup.  Taste and adjust the seasoning again right before serving.  You may also elect to beat in a bit more cream right before serving, to increase the silky richness of the dish.

Pure & Simple

“Such pure, clear flavor!” Mrs. Kitchen Riffs exclaimed as she took her first sip of soup.  “This is so tasty, it’s hard to believe you made it with just leeks, potatoes, and water.  Or did you substitute stock this time?”

“No stock,” I replied.  “Just water.  For years I used stock, and it makes a nice variation.  But I’ve finally decided this soup works better without it.”

“Who knew vegan could be so good?” asked Mrs KR.  “And this recipe is so simple!  Sometimes simple is best.”  She looked at me, grinning.

Actually, we both grinned.  Simple are us.

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