This rippled root vegetable gratin is a refined take on the classic comfort dish, with ultra-thin sweet potato, beetroot and white potato slices folded into soft, sculptural layers and baked in garlicky light cream cheese with thyme and Gruyère until golden and bubbling.
An adjustable mandolin is essential here to achieve slices thin enough to bend and ripple. It’s what creates the signature texture and look of this dish. I’ve linked the mandolin I use and recommend here for anyone wanting to recreate the effect at home.
This gratin is baked in a lidded casserole dish, which is ideal for recipes like this. The depth allows the rippled layers to sit snugly and upright, while the fitted lid helps the gratin cook evenly before finishing uncovered for a beautifully golden top. It’s the perfect size for entertaining and looks great straight from oven to table.
Shop the round casserole dish here
Rippled Rainbow Gratin
Ingredients
- 1 Tbsp extra virgin olive oil for greasing
- 600 g white potatoes washed (skin on)
- 600 g orange sweet potatoes skin on
- 600 g purple sweet potatoes peeled if needed
- 600 g beetroot peeled
- 400 ml light cream
- 5 cloves garlic finely minced
- Pinch freshly grated nutmeg
- Generous salt and freshly cracked black pepper
- 1 Tbsp fresh thyme leaves finely chopped
- 1 cup grated Gruyère cheese
- ⅓ cup finely grated Parmigiano Reggiano or parmesan cheese
- 1 Tbsp fresh chives finely chopped, to garnish
Instructions
- Preheat the oven to 180°C (fan-forced).
- Using a mandolin on the thinnest setting (ideally <1 mm), slice the white potatoes, orange sweet potatoes, purple sweet potatoes and beetroot into very thin slices. The slices should be flexible enough to fold and ripple but not too thin that they snap.
- Grease a shallow baking dish or French oven using olive oil
- Gently fold and wave the slices, layering them upright and snugly into the dish so they form delicate ripples. Alternate the vegetables to create a colourful layered effect. Season generously with salt and freshly cracked black pepper.
- In a jug, whisk together the light cream, garlic, nutmeg, thyme, salt and pepper.
- Sprinkle the Gruyère cheese over the top, then pour over your cream mixture.
- Finish with a sprinkle of parmesan cheese.
- Cover tightly with foil or a lid and bake for 60 minutes, until the vegetables are tender.
- Remove the cover and bake for a further 20 minutes, until golden and bubbling around the edges.
- Allow the gratin to rest for 10 minutes, then finish with chopped chives before serving
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