perfect potato leek soup

What makes a potato leek soup perfect?

It’s all in the texture. It should feel like velvet on the tongue, perfectly smooth and creamy.

When I was first learning to cook in my teens, experimenting in the kitchen with few skills and little knowledge, it occurred to me that if I whipped up my very good mashed potatoes in the food processor, they’d be even smoother and creamier.

I can see you grinning already …

What did I know about starch molecules???

The potatoes are a little more forgiving when submerged in stock and being puréed with sautéed leeks and onions, but still, you want to treat them gently. Respect the starch. Overwork your potatoes and your soup will have a gummy texture.

One way to avoid overworking potatoes is to put them through a ricer rather than using a blender or food processor. It takes a bit more effort, but the result is worth it.

That’s fine for making mashed, but when they’ve been cooked with leeks and onions, it’s harder to separate them out from the other stuff in the pot. I do purée this soup in the same way that I purée most of my smooth soups—with an immersion blender. The way I avoid overworking is by minimizing the amount of working that’s required. Rather than starting with my potatoes in chunks, as most recipes instruct, I begin by slicing them thinly. By the time they’re ready to be puréed, they’re already well on their way to velvety heaven.

You can use your wonderful homemade chicken stock as the foundation for this soup, but truth be told, a high quality boxed stock or broth does the job just as well. So, I recommend you save your homemade stock or broth for when you really want that flavor to dominate. I’m a big fan of Costco’s organic chicken broth.

Looking to make this soup kosher? We run into the same issue with any soup that starts with stock and finishes with milk or cream. The solution is an easy one. Instead of chicken stock, use your favorite no-chicken broth. Vegetable stocks in general vary greatly, depending upon what vegetables are used. Any stock that uses tomatoes or is dark in color is a no-no in this recipe. Try to find one of those that claim to be “chicken flavored,” and do go for one without artificial ingredients.

The delicate flavor of leeks sautéed in butter until they’re melting is a beautiful thing. That said, I find the addition of some onion gives the soup a little more zing without masking the flavor of the leeks. You can make this soup in advance. Just don’t add the milk and cream until you’re reheating it to serve.

Perfect Potato Leek Soup

Ingredients:

• 4 tablespoons (2 ounces) unsalted butter

• 6 large leeks—white part only

• 1 medium yellow onion

• 6 medium/large russet or Yukon gold potatoes (or some of each)

• 4 cups stock, chicken or no-chicken

• 1 tablespoon freshly squeezed lemon juice

• a few sprigs of fresh thyme

• 1 bay leaf

• 2 cups whole milk

• 3 cups heavy cream

• kosher salt and white pepper to taste

• snipped fresh chives or scallions for garnish

• optional: a gentle grating of nutmeg

Method:

• Cut the leeks in half, lengthwise, and then slice them crosswise into half rings. Put the sliced leeks into a large bowl of fresh cold water to clean them. Make sure you get all the bits of grit out from between the layers. Slice the onion thinly.

• Peel and thinly slice the potatoes.

• Melt the butter in a large soup pot and sauté the leeks and onions until very soft and beginning to turn golden.

• Add the potatoes, the stock, the bay leaf, the thyme, and the lemon juice, and simmer gently for 45 minutes.

• Remove the thyme sprigs and the bay leaf. Using an immersion blender on medium speed, purée the soup until smooth. Use quick, short bursts.

• Add the milk and the cream. You can reduce the amount of cream if you think you need to, but please don’t leave it out.

• Reheat the soup gently without boiling it and taste for salt. Season according to your taste.

• Ladle the soup into bowls and top each one with a few gratings of nutmeg and some chopped chives or scallions and serve.