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Potato and onion soup

Creamy and smooth with floral notes from fresh herbs, finished with sweet caramelised onions for an extra hit. This potato and onion soup recipe is ideal for using up a glut of homegrown potatoes.

  • 15 minutes prep. time
  • 1 hour cooking time
  • Serves 6
  • Soups, stews & curries, Vegetarian & vegan
A bowl of our potato and onion soup with an onion topping from a recipe in our Cookbook
Tasty potato and onion soup with a sautéed onion topping | © National Trust Images/William Shaw


  • 20ml vegetable oil
  • 750g onions, sliced
  • 3 garlic cloves, chopped
  • 10g fresh sage
  • 600g potatoes
  • 1 litre boiling water
  • 10g vegetable bouillon or 1 stock cube
  • Small sprig fresh thyme
  • 120ml milk

To serve

  • 2 tsp rapeseed oil
  • 100g red onions, finely sliced


Step 1

Peel the potatoes and cut into chunks.

Step 2

Place on a lined baking tray, add the sage and half of the oil and mix well. Cover and place into a preheated oven at 180°C (160°C fan/gas mark 4) for around 40 minutes, stirring occasionally, until soft and lightly coloured.

Step 3

Pour the oil into a heavy-based pan on a medium hob and add the onion and garlic.

Step 4

Sauté for 10 minutes until soft, reduce the heat and cover with a lid. Leave to sweat for a further 20 minutes. Remove the lid, increase the heat and allow to colour slightly.

Step 5

Add the potatoes to the onions and stir well.

Step 6

Add the water and the bouillon or stock cube and bring to a rapid boil. Continue to boil for a further 15 minutes until all the vegetables are soft.

Step 7

Remove from the heat and blend with a stick blender until perfectly smooth.

Step 8

Add the thyme leaves and the milk, season well to taste.

Step 9

For the topping 

Place the oil in a pan, add the sliced onions and sauté until soft. Place a spoonful on top of the soup when you serve.

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