Remove the roots and dark green tops from the leeks, and slice them into thin slices. Wash them well under running water to remove any soil or sand inside.
4 leeks
Peel and chop the onion and garlic.
1 onion, 2 garlic cloves
Peel and chop the potatoes too. I cut them slightly smaller than if I was making roast potatoes, as a guide.
800 g potatoes
Put all of the vegetables in the slow cooker pot.
Make up the vegetable stock and add it to the pot.
2 vegetable stock cubes, 1.2 litre water
Put on the lid and cook for 2-3 hours on high, or 6-7 hours on low.
Once the cooking time is up, use a knife to check that the potatoes are soft. Then blend – you can either use a hand or immersion blender in the pot or transfer the soup in batches to a food processor.
Season with salt and pepper to taste, if you like swirl a little sour cream through the soup and garnish with some chopped fresh herbs and serve with wholegrain bread for a filling and nutritious meal.