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French Leek and Onion Soup

I gotta say, when the plumber told us we’d have to dig up our front yard in a few years to replace the ancient, jacked-up, root-decimated sewer line, I felt a twinge of relief along with the massive wave of financial panic washing through my body.

Yeah, it’s going to be expensive. But it also means we’ll have to move the raised garden beds and I’ll have an excuse to call it quits on my failed gardening career.

I shouldn’t have built the beds in the first place. Virtually no part of our yard gets enough sunshine to truly grow vegetables to their full potential.

leek onion soup

The only hose spigot is on the back of the house, and my lazy ass gets really tired of dragging 100 feet of rubber down our sidewalk day in and day out, so by July I’ve pretty much abandoned it to the elements.

What I do manage to grow goes to the animals before I can grab it—our friendly neighborhood groundhog is a kale connoisseur and the deer sneak over in the middle of the night to nip the tops off any green beans that managed to twirl up their metal trellises.

And, I’m not kidding, the squirrels eat my garlic. New Jersey squirrels!

French leek and onion soup is a hearty comfort when the weather is less than perfect.
Photo: Casey Barber

My carrots are stubby, my peppers puny, my radishes nonexistent. The best thing I can do is to throw some leeks in the bed and leave them to overwinter as my eventual spring reward.

It’s true that I’ve never tried a summer-grown leek side by side with an overwintered one.

But word on the street (word on the farm?) is that leeks left in the ground throughout the fall and winter are sweeter and more flavorful than those who get yanked out of the garden during the warm months.

leeks for soup, via goodfoodstories.com
Photo: Casey Barber

For five years, I’ve been planting leeks and letting them bide their time through the subzero temperatures, waiting for that much-anticipated first week of 50-degree temperatures and soft, thawed ground to pull them out by their beardy roots.

Their unearthing means I can truly celebrate the sunny days ahead.

This year’s first snowstorm covered my leeks before I could get around to mulching them (yes, I am the typical procrastinating gardener), so my yield was a little sad and mushy this time around.

But I was able to salvage enough of my crop to make a hearty little pot of leek and onion soup before (I hope, I hope, I hope) the cold weather is gone for good.

French leek and onion soup
Photo: Casey Barber

It’s just French soupe à l’oignon, slow-simmered until it gives up the goods, but it really does gain more sweetness and a fuller flavor when verdant leeks enter the picture.

Might there be something to this overwintering thing after all? Let me have my small victories.

And in case you’re wondering how my cats celebrated this first week of real spring temperatures, they sat happily in a screened-in window watching robins, and Lenny killed a fly. To each his own.

leek onion soup

French Leek and Onion Soup

Yield: 4 servings
Prep Time: 20 minutes
Cook Time: 1 hour 10 minutes
Total Time: 1 hour 30 minutes

Leeks left out in the cold all winter become sweeter and more tender when eaten in the spring—like in this hearty French-style leek onion soup.


  • 1 pound leeks
  • 1 pound yellow or sweet onions
  • 2 medium to large garlic cloves
  • 1 tablespoon minced fresh sage leaves + mini sage leaves for garnish
  • 4 tablespoons unsalted butter
  • 1/2 teaspoon kosher salt
  • 1/4 teaspoon freshly ground black pepper
  • 1 quart beef broth
  • 1 small baguette
  • 1 cup coarsely grated Gruyère cheese


  1. Trim the leeks down to the tender white and green parts, slice them in half lengthwise, and let them sit in a bowl of cold water for 5-10 minutes to let any residual grit float out of their layers and into the bottom of the bowl. 
  2. Peel the onions, lop off the root and stem ends, then slice them in half lengthwise. Cut the onions into thin strips by slicing with the grain of the onion. I don't like overly long, stringy pieces of onion in my soup, so if I'm working with one particularly large onion, I'll often halve the strips again so they're no more than 3 inches long.
  3. Lift the leeks out of the cold water (don't pour them into a strainer; that'll just wash them with the grit you removed) and roughly chop them into 1/2-inch bits. 
  4. Peel and thinly slice the garlic.
  5. Melt the butter in a Dutch oven or heavy-bottomed saucepan over medium heat. 
  6. Add the onions, leeks, garlic, minced sage, and salt. Stir to combine and cover halfway with a pan lid so steam can escape.  
  7. Cook, stirring frequently, for about 45 minutes. The leeks and onions will soften completely and deepen in color; if they start to caramelize too quickly, lower the heat.
  8. Remove the lid and cook the vegetables for 10 minutes more to let some of the moisture burn off. 
  9. Add the broth and bring to a simmer. 
  10. Cook for 15-20 minutes (but hey, you could let it go for a half hour or more if you want it the liquid to reduce and for it to be more of a leek stew mess. I'm not judging.)
  11. While the soup simmers, slice the baguette into rounds at least 1/2 inch thick and determine how many you'll need to cover the diameter of your soup bowl. 
  12. Toast the baguette rounds until golden and crispy.
  13. Ladle the soup into the oven-safe bowls and top with the toasted rounds. 
  14. Top each with a healthy handful of Gruyère and broil until the cheese is melted and bubbling. (Watch as it broils to make sure the toast doesn't burn!)
  15. Garnish with mini sage leaves, if desired, and serve immediately.
Nutrition Information:
Yield: 4 Serving Size: 1
Amount Per Serving: Calories: 557Total Fat: 26gSaturated Fat: 15gTrans Fat: 0gUnsaturated Fat: 9gCholesterol: 69mgSodium: 1914mgCarbohydrates: 60gFiber: 4gSugar: 12gProtein: 24g

The nutritional information above is computer-generated and only an estimate.

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  1. I am a lazy gardener, too. I always start with grand plans and aspirations of greatness, but by August I’m tired of waiting for tomatoes and am pissed off at all the rabbits and squirrels that inexplicably eat one bite of each before throwing it to the ground.

    I do wish I hate overwintered leeks, though. Perhaps I’ll just do that this year in one whole raised bed. Leeks for all.

    Can I come over for a bowl of soup?

    1. You have some picky critters up there – our New Jersey rodents are totally cool eating the entirety of the vegetables they find. (Except the leeks, hooray!)

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