Most slow cooker recipes trade taste for convenience—but this Slow Cooker Potato Leek Soup gives you both. It’s an easy dump-and-go recipe that almost cooks itself. Slow cooker soups can taste flat, so we add tangy buttermilk to make the flavors shine. The buttermilk does double duty—it adds flavor while using less cream, so the soup stays rich, cozy, and healthier than most.
If you’re looking for a stovetop version, make my Vegan Potato Leek Soup—it's dairy-free but nobody would guess it. Slow Cooker Pumpkin Soup is another great soup to try this fall or winter. Visit my full collection of soup recipes—or check out the Evergreen Kitchen cookbook, which has 14 deliciously healthy soups and 100+ weeknight dinner recipes!
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Why you'll love this recipe
- Easy to make: Just 10 minutes to prep—made with real, easy-to-find ingredients.
- Weeknight favorite: Perfect for busy days! Toss in the slow cooker in the morning, then come home to dinner ready.
- Smarter slow cooking: Slow cookers make life easy, but flavor can fall flat. This recipe fixes that with one simple “secret ingredient” that keeps every bite bright and flavorful.
- Not too thick: Can I let you in on a secret? A great potato leek soup shouldn't be super thick or gummy. A common mistake is over-blending potatoes. This recipe uses just the right ratio of liquids and a method to ensure your soup blends up light and smooth.
- Customizable: Keep it classic, or add your favorite toppings like chives, a drizzle of cream, or Air Fryer Croutons.
- Make-ahead friendly: Like many of my soup recipes, leftovers taste even better!
Ingredients (and substitutes)
This silky smooth Slow Cooker Potato Leek Soup has just 9 ingredients—plus salt and pepper. Here's what you need to make this recipe:
- Leeks: Use only the white and light green parts of the leeks for a smooth, delicate flavor.
- Potato: Russet potatoes are my favorite, because they're starchy and break down easily. This means less blending, so your soup doesn't get gluey and thick. You can substitute Yukon Gold potatoes. Just take extra care to not over-blend them.
- Broth: Since the ingredient list is short, a good broth really matters. I love using Better Than Bouillon No Chicken Base for its savory flavor, but vegetable broth works too. Or, chicken broth if you're not vegetarian.
- Buttermilk: Once you try potato leek soup with buttermilk, you'll never go back! Buttermilk's tang really makes the flavors really pop. Since slow cookers tend to dull flavors, adding a bit of acidity makes a big difference.
- Cream: Adds a silky, luxurious finish. Since the buttermilk brings so much flavor, you only need a small splash of cream—making this soup lighter than most. I tested a version without cream, but the touch of cream balances the tangy buttermilk just right.
Find the recipe card below for the complete recipe, including all ingredients and instructions.
Want more popular potato recipes? Don't miss Air Fryer Breakfast Potatoes, Crispy Smashed Fingerling Potatoes, and Grilled Potato Salad.
How to make Slow Cooker Potato Leek Soup
This Potato Leek soup is a dump and go slow cooker recipe. So, it couldn't be any easier to make! Here's how:
1. Add all the ingredients (except buttermilk and cream) to a slow cooker.
2. Cover and cook for 3 to 4 hours on "high" or 6 to 8 hours on "low".
3. Remove bay leaf, then blend just until smooth (ideally no more than 1 minute).
4. Stir in buttermilk and cream. Taste and season with more salt, if needed. Serve.
Find the recipe card below for the complete recipe, including all ingredients and instructions.
Tips
- Peel the potatoes: This ensures a silky smooth soup—and only takes a couple minutes.
- Trick for cleaning leeks: Leeks often trap dirt between their layers. To remove all the dirt—you can slice the leeks into half-moons, then swish them around in a big bowl of cold water. Use a colander to drain well then go ahead and use as directed.
- Use a great vegetable broth: Since this soup comes together with so few ingredients, it's important to use a flavorful broth for best results. I recommend a vegan "chicken" broth, but another high-quality vegetable broth works too. Better Than Bouillion is my go-to.
- Use an immersion blender if you have one: An immersion blender allows you to blend the soup directly in the slow cooker. It's fast and makes fewer dirty dishes! But a countertop blender works too.
- Don't over-blend the soup: Potatoes can get gluey when over-mixed (same goes with mashed potatoes). Blend only for as long as is needed for the soup to become smooth. It shouldn't take longer than a minute.
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Topping Ideas
Potato Leek Soup is delicious plain—but it's even better with toppings! Here are some of my favorites:
- Cream: This is an easy garnish, since it's already an ingredient in the soup. To make a pretty looking swirl, use a spoon to drizzle the cream in a circular motion on top of the soup. Then drag a toothpick or chopstick through the cream to create swirls.
- Croutons: These Air Fryer Croutons are amazing on top of soup!! They're crunchy, salty, perfectly spiced—as one reader says: "the best croutons I've ever made!".
- Fried Leeks: You can thinly slice and fry the dark green parts of the leeks for crispy, savory topping. It's a great no-waste garnish that looks and tastes delicious.
- Crispy Shallots: Storebought fried shallots (or onions) are a fast way to add crunch.
Recipe FAQs
I prefer russet potatoes for classic flavor and a whiter color. You can easily substitute Yukon Gold potatoes instead—your soup will just be a bit more yellow.
It's up to you! Personally, I find many potato leek soups to be too thick—almost gluey. This happens when potato soup is over-blended, releasing the starch, which starts to develop a thick, gluey mouthfeel. This recipe creates a silky smooth, but not super thick soup. If you prefer a thicker soup, you can reduce the broth slightly. Avoid reducing it too much because your soup will thicken very quickly when blended.
I highly recommend you make my Vegan Potato Leek Soup recipe instead. It's been developed to also have a silky (not thick and gluey) consistency—and the bright "buttermilk" flavor, but without any dairy.
Leftovers keep in the fridge for up to 4 days.
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📖 Recipe
Slow Cooker Potato Leek Soup
Ingredients
- 4 cups chopped leeks (white & light green parts only) (2 large leeks, 1.25 lb before trimming)
- 1 lb peeled and chopped russet potatoes (2 potatoes, see note 1)
- 4 cups vegan chicken broth (or vegetable broth, see note 2)
- 2 tablespoons butter
- 3 cloves minced garlic
- 1 teaspoon fine sea salt
- ¼ teaspoon black pepper
- ⅛ teaspoon ground nutmeg
- 1 dried bay leaf
- 1 cup buttermilk (full-fat recommended)
- ⅓ cup whipping cream (or heavy cream)
Instructions
- Combine: Add 4 cups chopped leeks (white & light green parts only), 1 lb peeled and chopped russet potatoes, 4 cups vegan chicken broth , 2 tablespoons butter, 3 cloves minced garlic, 1 teaspoon fine sea salt, ¼ teaspoon black pepper, ⅛ teaspoon ground nutmeg, and 1 dried bay leaf to a slow cooker. Stir to mix.
- Cook: Cover with lid and cook for 3 to 4 hours (on high) or 6 to 8 hours (on low).
- Finish: Use an immersion blender to blend the soup directly in the slow cooker; or carefully transfer soup to a blender and blend in batches, if needed (see note 3). Blend only until smooth—about 1 minute—because over-blended potato leek soup gets gummy. Stir in 1 cup buttermilk and ⅓ cup whipping cream. Taste and add more salt and/or whipping cream if needed. Ladle soup into bowls and garnish, if desired (see note 4).
Notes
- Potatoes: About 2.5 cups chopped. Russet Potatoes recommended, otherwise substitute Yukon Gold.
- Broth: A great tasting broth makes a big difference here! I prefer Better Than Bouillon No Chicken for this recipe, but Better than Bouillon Vegetable works too. If you're not vegetarian or vegan, you can use regular chicken broth.
- Blending soup: Potatoes can get gluey/gummy when over-blended. Stop blending as soon as the soup is creamy; and avoid blending longer than 1 minute. Always exercise caution when blending hot liquids! If transferring to a countertop blender, make sure not to overfill the container and blend in batches if needed. And make sure the blender has a vented lid, which allows steam to escape when blending hot liquids.
- Garnish ideas: Chopped chives, Drizzle of cream or buttermilk, Air Fryer Croutons, Crispy Shallots/Onions, Fried Leeks, Freshly cracked black pepper, and more!
- Storage tip: Keeps in the fridge for 3 to 4 days.
- Yield: Makes 8 to 9 cups soup. Nutritional estimate assumes 2 to 2.25 cups per serving.
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