Onion Leek Soup

Onion Leek Soup is a warm, comfy soup recipe flavored with garlic, sage, thyme, and bay leaves. Sauté the ingredients first for added flavor and don’t forget to save the green parts of the leeks! They are a satisfying topping. Nothing goes to waste in this vegan and paleo soup recipe! {Vegan + Paleo}

If you need a warm and comforting soup that stands on its own as a light meal, then look no further than Onion Leek Soup. And if you’re making a heartier meal and need a sidekick, Onion Leek Soup is still up to the challenge. It really does go with just about every light or hearty meal, including these savory treats:

• Lemon Baked Chicken
• Oven-Roasted Turkey Breast
• Garlic Butter Steak Bites
• Broccoli Beef Stir-Fry
• Seared Garlic Scallops

Spiriteds, Onion Leek Soup is like a warm hug, and it will fit into your menu wherever you need it to! The sky’s the limit. Dip your favorite bread in it or break a handful of chips over the top as a garnish. I top my soup with cashews or sautéed leeks (the green parts!). Alternatives to the alternatives include a handful of sautéed cauliflower florets or other veggies, as desired.

But let’s take a step back and admire the leeks, shall we? I, for one, haven’t cooked with leeks before, and now I plan to add them to everything! Like collard greens and kale, once the green parts of the leeks are cooked, even for a few minutes, they go from tough and bitter to soft and savory. Seriously, if you haven’t already, it’s time to get your leeks on!

I modified this soup from an Onion Leek Soup recipe in Carol Heding Monson’s The Complete Slow Cooker Cookbook. It’s the perfect paleo and vegan soup recipe on chilly fall and frigid winter days! K-Hubs says it tastes like Thanksgiving. I completely agree. And because this soup is made in a slow cooker, the leg work is minimal. Although you can cook it for as little or as long as you want, I usually err on the side of four to six hours. This provides enough time for the flavors to intensify without turning the onions to mush.

I also add tapioca flour at the beginning of the cooking process to thicken up the soup, but that is entirely optional. However, I wait until the end of the cooking process to add extra salt and pepper. That way I don’t overdo it and family members can salt and season to their own heart’s desire.

If you’re ready to make a delicious light vegetable soup recipe, then grab your sauté pan, start up the slow cooker, and get simmering! Onion Leek Soup is just waiting to be made!

Onion Leek Soup ingredients

Here is the list of ingredients you’ll need to make Onion Leek Soup.

• Leeks. Separate the green part from the white part but don’t throw anything out! Each section can be used in this recipe, albeit in different steps.
• Onions. Any color. I use a combination of white and red onion, cut into wedges.
• Olive oil. Enough to cover the bottom of the sauté pan.
• Garlic cloves. Pressed or minced.
• Broth. Vegetable broth is my favorite for this recipe, but you can also use Bone Broth or Beef Broth. If you don’t have enough broth to cover four cups, then make up the difference with water.
• Tapioca flour. Add 3-4 tablespoons to the soup to thicken it, if desired.
• Bay leaves. Three or four.
• Fresh herbs. Sage leaves and thyme sprigs.
• White pepper, coarse black pepper, and sea salt. For the most part, these ingredients are to taste.
• Optional: White wine vinegar. A tablespoon and a half. This will sweeten the soup, so if you want it full-on savory, then I suggest omitting the vinegar altogether. 

NOTE: You can also garnish with dried sage, thyme, onion salt/powder, and garlic salt/powder in addition to the fresh versions. Dried herbs and seasonings sometimes taste different than their fresh counterparts, so I like to infuse my broths and oils with fresh ingredients and then finish off the recipe with dried versions.  

How to make Onion Leek Soup

Sauté, slow cooker, and sauté again. The extra sauté is optional but highly suggested. 🙂

1. Cut the onions into wedges, press or mince the garlic, slice the white parts of the leeks, and combine them in a large sauté pan with the olive oil and a pinch of sea salt. Sauté until cooked through, about 5-7 minutes. Transfer the sauté mixture to a slow cooker and pour in the broth and vinegar, if including, and add the bay leaves, sage leaves, thyme sprigs, and white pepper. For a thicker, pearlescent consistency, add 3-4 tablespoons tapioca flour. Cook on HIGH for 4-6 hours (preferred) or MEDIUM for 6-8 hours.
2. When the soup is done cooking, sauté the green parts of the leeks in olive oil and a pinch of sea salt in a small skillet. While the green portions are cooking, remove the bay leaves and thyme sprigs from the soup prior to serving. Pour the soup into bowls, garnish with sautéed leeks or other optional toppings, and sprinkle with salt, pepper, and other seasonings to taste.
3. Refrigerate leftovers for up to three days.

NOTE: Slice the white portions of the leeks either in rounds or lengthwise (pictured). If you plan to sauté the green parts, then slice them at an angle (pictured).

Can you eat the green part of the leek?

Yes, you can. But it helps to cook them first. According to Allison Robicelli in her Taste article, Don’t Throw Out the Leek Greens, even a simple sauté is enough to soften them. For this recipe, I sautéed the green parts of the leeks once the soup was ready to eat. By the time the sauté was done, the soup had cooled enough to eat.

Tips for making this soup

Below are tips to help you get the most out of your Onion Leek Soup!

• Add the fresh thyme sprigs in bunches, rather than small, detached pieces. This will make it easier to fish them out when the cooking process is complete.
• For soft onions that aren’t mushy, set your slow cooker to no more than six total hours of cook time.
• To prevent the tapioca flour from clumping when added to the broth, add it in small batches before the broth has heated up in the slow cooker and stir everything together with a fork.

Get your slurp on!

If it’s soup you want, then check out these delicious, slurp-worthy vegetable soups!

• Dairy-Free Creamy Broccoli Soup
• Homemade Vegetable Broth
• Dairy-Free Homemade Creamy Vegetable Soup
• Cinnamon, Sweet Potato, and Carrot Soup
• Creamy Roasted Garlic and Onion Soup

Spiriteds, I hope this blog post finds you well. Take care of yourselves, stay safe, and know that I’m glad you’re here. ❤️

This recipe was adapted from The Complete Slow Cooker Cookbook. Munson Heding, Carol. Main Street. New York. 2003, pg. 20.

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