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Potato & Celery Root Gratin with Leeks

Peer reviewed by UK recipe editorsAuthored by UK recipe editorsOriginally published 28 Jan 2026

Meets Patient’s editorial guidelines

This indulgent potato and celeriac gratin is a sophisticated twist on the classic dauphinoise. By combining earthy celery root with floury potatoes and sweet, softened leeks, you create a side dish with wonderful depth of flavour. The cream is infused with garlic and thyme before baking, ensuring every layer is thoroughly seasoned, while a generous topping of nutty Gruyère cheese provides a beautifully golden, bubbling crust.

As a hearty vegetarian dish, this gratin is an excellent accompaniment to a traditional Sunday roast or a festive centrepiece. The celeriac adds a subtle, nutty fragrance that lightens the richness of the double cream, making it a favourite for autumn and winter dining. It can even be prepared a few hours in advance and reheated, leaving you more time to spend with your guests.

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Ingredients for Potato & Celery Root Gratin with Leeks

  • 725ml double cream

  • 2 garlic cloves, peeled

  • 1 sprig thyme plus 3 teaspoons fresh thyme leaves, divided

  • 2 tablespoons (1/4 stick) unsalted butter, divided

  • 3 leeks, white and pale-green parts only, halved lengthwise, thinly sliced crosswise

  • Kosher salt

  • 900g russet potatoes, peeled, very thinly sliced crosswise (1/8" thick)

  • 450g celery root, peeled, very thinly sliced crosswise (1/8" thick)

  • 300g grated Gruyère

  • Freshly ground black pepper

How to make Potato & Celery Root Gratin with Leeks

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Preheat oven to 177°C. Heat cream, garlic, and thyme sprig in a medium saucepan just until bubbles begin to form around edge of pan. Remove from heat; set aside to steep.

Melt 1 tablespoon butter in a medium skillet over medium heat. Add leeks; season with salt and cook, stirring often, until tender (do not brown), 10-12 minutes. Transfer to a small bowl and set aside.

Butter a 3-quart gratin dish with remaining 1 tablespoon butter. Layer 1/3 of potato slices and 1/3 of celery root slices evenly over bottom of baking dish. Cover with 1/3 of leeks, then 1/3 of Gruyère. Sprinkle with salt, pepper, and 1 teaspoon thyme leaves. Repeat layers twice more. Strain cream mixture into a medium pitcher and pour over vegetables.

Set gratin dish on a large rimmed baking sheet and cover tightly with foil. Bake for 1 hour. Carefully remove foil; continue baking until top is golden brown and sauce is bubbling, 25-30 minutes. DO AHEAD: Can be made 2 hours ahead. Let stand at room temperature. Tent with foil and rewarm in a 300° oven until hot, about 20 minutes.

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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