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Mashed Potatoes and Parsnips With Caramelized Onions and Blue Cheese

This mashed potato and parsnip recipe offers a sophisticated twist on a classic British side dish. By combining earthy parsnips with fluffy potatoes, the base gains a subtle sweetness that perfectly complements the rich, savoury notes of the blue cheese. The addition of slow-cooked caramelised onions provides a deep marmalade-like texture, while fresh thyme cuts through the richness with a hit of herbal fragrance.

As a high-protein vegetable dish, this mash is more substantial than your typical Sunday roast accompaniment. The use of chicken broth instead of heavy butter ensures a silky consistency without being overly cloying. It is the perfect partner for grilled steaks, roasted poultry, or even as a comforting base for a vegetarian mushroom ragout. This homemade side is a simple way to elevate your midweek meals with bold, punchy flavours.

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Ingredients for Mashed Potatoes and Parsnips With Caramelized Onions and Blue Cheese

  • 1 tablespoon olive oil

  • 3 large white onions, thinly sliced

  • 2 tablespoons brown sugar

  • 1/4 teaspoons salt

  • 3 baking potatoes (such as Yukon gold, about 900g ), peeled and cubed

  • 6 parsnips (about 1 lb), peeled and cut into 1-inch pieces

  • 350ml low-sodium chicken broth, heated

  • 60ml crumbled blue cheese

  • 3 tablespoons fresh thyme, chopped

Heat oil in a large skillet over high heat; reduce to medium. Cook onions with sugar and salt, stirring occasionally, until onions brown, 20 to 25 minutes. Add a few tablespoons water as you cook to keep onions from sticking or burning. Fill a medium stockpot 3/4 full with cold water. Add potatoes and parsnips; bring to a boil over high heat. Reduce heat and simmer until potatoes and parsnips are fork-tender, 20 to 25 minutes, then drain. Beat 1/4 of potato parsnip mixture and 90g broth in a mixing bowl with an electric mixer on medium speed until smooth. Repeat, alternating between potato-parsnip mixture and broth, until you've incorporated all. Fold in onions, cheese and thyme, and serve.

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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