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Walla Walla Onion, Pine Mushroom Fonduta

This elegant vegetarian dish transforms humble sweet onions into a sophisticated centrepiece. By slow-roasting the onions on a bed of salt, their natural sugars caramelise, creating a tender vessel for a rich, earthy filling. The combination of wild pine mushrooms and melted Gruyère cheese creates a luxurious fonduta that is both comforting and deeply savoury, making it an ideal choice for a decadent starter or a light seasonal supper.

Preparing this homemade onion and pine mushroom fonduta is a wonderful way to celebrate autumnal flavours. The addition of torn sourdough into the filling provides a rustic texture that soaks up the creamy sauce beautifully. Serve these stuffed onions with thick slices of crusty bread to catch every drop of the melted cheese and mushroom liquor for a truly satisfying dining experience.

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Ingredients for Walla Walla Onion, Pine Mushroom Fonduta

  • 4 Walla Walla (sweet) onions (about 450g each)

  • 150g coarse salt, for roasting

  • 120ml extra virgin olive oil

  • 475ml peeled, washed, and thinly sliced pine mushrooms

  • 60ml plain flour

  • 475ml Vegetable Stock

  • 120ml double cream

  • Reserved chopped innards from onions

  • 2 tablespoons thyme leaves Kosher salt

  • Fresh-ground black pepper

  • 150g small torn pieces day- old Arctic Sourdough

  • 230g grated Gruyère-style cheese (we like Farm House Natural Cheeses Heidi)

  • 120g grated Gruyère-style cheese

  • Arctic Sourdough

Preheat the oven to 232°C.

Cut the very tops (about 1 inch) off the onions and then replace. Make a bed of coarse salt in a small roasting pan. Place the onions on the salt and roast for about an hour, or until soft through.

When cool enough to handle, scoop out the insides of the onions, leaving the outer two layers intact within the skin. Take care not to scrape out the base of the onions, as the fonduta will leak out the bottom. Finely chop half of the onion innards for the filling. Set aside.

In a medium-size sauté pan, heat the olive oil and add the sliced pine mushrooms. Sweat for 5 minutes, then add the flour. Sauté for 1 minute more, then add the Vegetable Stock and cream. Bring to a simmer and add the reserved chopped Walla Walla, thyme, and salt and pepper to taste. Add the day-old sourdough bread pieces. Cook together for 5 minutes to meld the flavours. Add the grated Gruyère, stirring to melt, then remove f rom the heat.

Preheat the oven to 232°C. Place the Roasted Walla Walla Onions in a roasting pan, and fill with hot Pine Mushroom Fonduta (if you have extra, it can be served on the side). Top with the grated Gruyère. Roast for 10 minutes, until bubbly.

Serve with lots of Arctic Sourdough and any extra fonduta that didn’t fit in the onions.

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.

  • 28 Jan 2026 | Originally published

    Authored by:

    UK recipe editors

    Peer reviewed by

    UK recipe editors
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