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Roasted Japanese Sweet Potatoes with Spring onion Butter

This roasted Japanese sweet potato dish is a masterclass in balancing sweet and savoury flavours. By roasting the potatoes at a high temperature, the natural sugars caramelise while the flesh becomes incredibly tender and creamy. The addition of a white miso and spring onion butter provides a salty, umami-rich contrast that elevates this simple root vegetable into something truly special.

Ideal as a nutritious vegetarian main or a substantial side dish, these potatoes are naturally filling and packed with vitamins. The umami-rich miso butter can be prepared in advance, making this an easy option for a midweek dinner or a relaxed weekend lunch. Serve them alongside a crisp green salad or roasted purple sprouting broccoli for a vibrant, balanced meal.

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Ingredients for Roasted Japanese Sweet Potatoes with Spring onion Butter

  • 8 small slender Japanese or Garnet sweet potatoes (4 to 2.3kg total)

  • 1 1/2 sticks unsalted butter, well softened

  • 1 1/2 tablespoons miso paste (preferably white)

  • 3 tablespoons finely chopped spring onion

How to make Roasted Japanese Sweet Potatoes with Spring onion Butter

Preheat oven to 232°C with rack in upper third.

Prick potatoes all over with a fork and put on a foil-lined large baking sheet. Bake until very soft when squeezed, 45 minutes to 1 hour.

While potatoes bake, stir together butter, miso, and spring onion until combined.

Slit hot potatoes lengthwise and, using oven mitts, push in sides to puff up potato. Serve with some spring onion butter in centre of each and with additional spring onion butter on the side.

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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