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Three Onion Soup

This aromatic three onion soup is a sophisticated take on a comforting classic, combining the distinct flavours of leeks, shallots and traditional onions. By slowly caramelising the vegetables until golden and deglazing the pan, you create a deep, savoury base that is naturally sweet and satisfying. The addition of diced potatoes provides a velvety body without the need for thickeners, making it an excellent choice for those seeking a lighter, homemade meal.

As a dairy-free dish that can easily be adapted for vegetarians using vegetable stock, this versatile soup fits perfectly into a healthy weekday routine. The final garnish of sharp balsamic vinegar and a sprinkle of Gruyère adds a professional touch, balancing the earthy notes of the onion broth. Serve it with a slice of crusty sourdough for a nutritious and warming lunch.

Continue reading below

Ingredients for Three Onion Soup

  • 4 medium leeks

  • 1 teaspoon olive oil

  • 1 small onion (110g ), thinly sliced

  • 2 large shallots (110g ), thinly sliced

  • 350ml water

  • 1 large boiling potato (170g) such as Yukon Gold

  • 240ml nonfat chicken broth

  • 120ml grated Gruyère (60g)

  • 2 teaspoons balsamic vinegar

How to make Three Onion Soup

Chop enough white and pale green parts of leeks to measure 475ml . Wash leeks well in a bowl of cold water. Lift from water and drain in a colander. Heat oil in a 10-inch nonstick skillet over moderate heat until hot but not smoking, then cook chopped leeks, onion, and shallots with salt and pepper to taste, stirring frequently, until edges are golden brown, about 15 minutes. Add 120ml water and deglaze skillet, scraping up brown bits. Transfer mixture to a saucepan.

Peel potato and cut into 1/2-inch cubes. Add potato, broth, and remaining cup water to onions. Simmer, covered, stirring occasionally, until potatoes are very tender.

Puré;e 1‚ cups soup in a blender (use caution when blending hot liquids) and stir into remaining soup. Season with salt and pepper.

Serve soup sprinkled with cheese and drizzled with vinegar.

Disclaimer

While every effort has been made to ensure the information is accurate and up to date, individual needs may vary and dietary requirements can differ based on personal health conditions. Always check food labels and allergen information before preparing or consuming any recipe. If you have specific health concerns, allergies, intolerances, or are following a medically prescribed diet, seek advice from your GP, pharmacist, or a registered dietitian before making significant changes to your diet or lifestyle.

Article history

The information on this page is peer reviewed by qualified clinicians.

  • 17 Jan 2026 | Originally published

    Authored by:

    UK recipe editors

    Peer reviewed by

    UK recipe editors
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