Leek and Potato Slow Cooker Soup

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Leek and potato soup is such a classic. It really is a bit more of a wintertime soup – but I was looking to use up what I had in the fridge (and food deliveries are hit and miss right now amidst COVID lockdown). I could happily eat warm soups all year round anyway! Since I’m working from home and trying my sincere hardest to not get distracted, I decided to make a souper (get it) easy slow cooker leek & potato soup that I could make in the morning and simply finish off at lunchtime rather than needing to break to make a full meal.

Leek And Potato Slow Cooker Soup

How to make leek and potato soup

Leek and potato soup can be easily made in the slow cooker or on the hob – and the steps are very similar. Cook the leeks and potato in stock with herbs and garlic and then blend once everything has softened and the flavour has infused. I use dried thyme in this recipe (but you could easily use fresh – I am just struggling to get my hands on decent quality fresh herbs right now). You could swap that out for any type of herb that you fancy though!

Once the soup has cooked then use a stick/immersion blender to mix everything and then stir in some cream and butter. I use sour cream for this recipe to make it a little healthier.

How to thicken soup made in the slow cooker?

Sometimes cooking in the slow cooker does make things a little more watery than expected, since none of the liquid evaporates. I think personal preference comes into play a lot when judging these things too.

While this soup recipe should give you a great consistency (as I have tried and tested this a few times), if you do feel you need to thicken things up then try the following:

  1. Prevention can be better than cure. Before you blend, pour out some of the liquid into a separate bowl and blend the remainder (with all the lovely cooked potatoes and leeks). Then add the liquid in slowly until you reach the right consistency.
  2. If you’ve already blended the soup and it’s too thin then you can use cornstarch to thicken. Mix 1 tablespoon of cornflour with a couple of tablespoons of water in a small bowl and mix well. Slowly add to the soup and stir until you reach the right consistency. Note that you need to heat cornflour enough for it to thicken properly. Therefore it’s best to pour the liquid into a saucepan, bring until it’s just about to boil and then remove from the heat and stir well.
Slow Cooker Soup Leek and Potato

Can you freeze it?

Leek & potato soup is perfect for freezing. Simply pour into a freezer-proof container and place in the freezer for up to 3 months. Defrost before reheating and you can heat it up either in the microwave or in a pan on the hob.

How many calories are in this soup?

Slow cooker leek & potato soup has 400 calories per portion. It is pretty healthy all round. The ingredients are pretty clean (particularly if you use low sodium or freshly made vegetable stock). The recipe uses some butter to make it richer and creamier – and also some sour cream. If you want to reduce calories then you could replace the butter with more sour cream. Or you could replace both with low-fat yoghurt which also works great.

If you are looking for more great soup recipes then try this sweet potato & horseradish soup, or this butternut squash soup with honey creme fraiche.

Products that work great for this recipe

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Leek and Potato Slow Cooker Soup

Slow Cooker Leek & Potato Soup

  • Author: caroline
  • Total Time: 4 hours 10 minutes
  • Yield: 1 1x


Creamy, delicious, healthy and so so easy to make! Perfect for lunch with some crusty bread.

Makes one portion


  • 120g floury potatoes, such as maris piper – cut into 1 inch pieces
  • 100g leek – white and light green parts, roughly sliced
  • 300ml vegetable stock
  • 1/2 tsp dried thyme
  • 1 clove garlic – crushed
  • 2 tsp butter
  • 2 tsp sour cream
  • fresh herbs to garnish


1. Place the potatoes, leek, stock and garlic into the slow cooker. If you are using dried thyme then add that in now.

2. Cook on high for 4 hours or low for 7-8 hours. If you are using fresh thyme then add that around 15 minutes before the end of the cooking time. 

3. Use an immersion/stick blender to whiz the soup into a smooth consistency. Stir in the sour cream and butter and mix well. 

4. Serve with some freshly chopped herbs on top (parsley or chives work well), a drizzle of sour cream and some freshly milled black pepper. 

  • Prep Time: 10 minutes
  • Cook Time: 4 hours
  • Category: Soup
  • Method: Slow Cooker
  • Cuisine: British


  • Serving Size: 1
  • Calories: 400
  • Fat: 8g
  • Carbohydrates: 70g
  • Protein: 6g

Keywords: soup, leek, potato, lunch, british, slow cooker

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