Celeriac Dauphinoise (Keto Potato Gratin Swap)
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This celeriac dauphinoise is a keto swap for potato gratin: thin slices of celeriac simmered in garlic and thyme cream, then baked under a light Parmesan crust. Each of the 6 servings has 5.3g net carbs and 320 kcal. It takes 20 minutes to prepare and 1 hour 10 minutes to cook, plus 10 minutes to rest.
Celeriac dauphinoise is the side we reach for when a roast needs something rich and creamy in place of potatoes. This version is built on some well-loved recipes. Suzie Lee's celeriac and potato dauphinoise on BBC Food warms the cream with garlic and herbs, coats the slices in it before layering, and bakes the dish under baking paper before adding Parmesan to brown the top. Sophie Godwin's celeriac dauphinoise on BBC Good Food uses celeriac on its own, with garlic and thyme tucked between thin slices. On Reddit, an r/ketorecipes thread asks whether a keto potato dauphinoise is possible, and in a roast dinner thread on r/ketouk the top reply recommends celeriac dauphinoise alongside the meat. Our keto dauphinoise uses celeriac only, simmers the slices in the cream for 5 minutes so they bake evenly, and finishes with a thin Parmesan crust.
It suits a Sunday roast and Christmas dinner alike. Our keto Christmas dinner guide covers the rest of the plate, from the turkey to the sprouts.
What you need: this keto dauphinoise uses just celeriac, double cream, whole milk, garlic, thyme, nutmeg and Parmesan. No special ingredients.
Celeriac dauphinoise vs potato dauphinoise
Celeriac is a root vegetable from the celery family, and it contains much less starch than potato. Per 100g raw, UK data gives celeriac 2.3g carbohydrate and potato 19.6g. Made with the same cream, milk and cheese, a serving of celeriac dauphinoise has 5.3g carbohydrate, against 26.9g for a potato version.
| Food | Carbohydrate | Sugars | Net carbs |
|---|---|---|---|
| Celeriac dauphinoise, 1 serving | 5.3g | 4.3g | 5.3g |
| Same recipe with potatoes, 1 serving | 26.9g | 3.2g | 26.9g |
| Raw celeriac, 100g | 2.3g | 1.8g | 2.3g |
| Raw potato, 100g | 19.6g | 0.9g | 19.6g |
Celeriac and potato figures are UK CoFID 2021 data for "Celeriac, raw" (13-219, 2.3g carbohydrate and 1.8g sugars per 100g) and "Potatoes, old, raw, flesh only" (13-489, 19.6g carbohydrate and 0.9g sugars per 100g). The potato row is our recipe worked out with 750g of peeled potatoes in place of the celeriac, with the same cream, milk, garlic, thyme, butter and Parmesan. There are no polyols in any of them, so net carbs are the same as carbohydrate.
Tips for the best celeriac dauphinoise
- Peel it thickly. Celeriac skin is knobbly and full of roots. Cut the top and bottom off, sit it flat and cut the skin away in strips with a sharp knife. A 1kg celeriac gives about 750g once peeled.
- Slice it thin and even. About 3mm is right. A mandoline is quickest, but always use the hand guard. Slices of different thickness cook at different speeds.
- Simmer the slices first. Five minutes in the hot cream starts the celeriac softening and thickens the sauce a little, so the dish bakes evenly and the layers come out tender all the way through.
- Use double cream. It is less likely to split during a long bake than single cream. If an American recipe asks for heavy cream, our guide to whether double cream is the same as heavy cream explains the UK swap.
- Check it is tender. A knife should slide through the middle with no resistance. If the top browns before that, cover it loosely with foil and give it a little longer.
- Let it rest. Ten minutes out of the oven lets the cream settle, so each portion holds its layers on the plate.
Celeriac Dauphinoise (Keto Potato Gratin Swap)
- Prep time20 min
- Cook time1 hour 10 min
- Total time1 hour 40 min, including resting
- Serves6 as a side
- Net carbs5.3g per serving
Ingredients
- 15g unsalted butter, softened, for the dish
- 1 large celeriac (about 1kg), to give 750g once peeled
- 300ml double cream
- 150ml whole milk
- 2 garlic cloves, crushed
- 2 tsp fresh thyme leaves, plus a few sprigs to serve
- A good grating of nutmeg
- ¾ tsp fine sea salt
- Black pepper, to taste
- 40g Parmesan, finely grated
You will also need a mandoline or a large, sharp knife, a large, wide pan and a 1.5 litre ovenproof dish.
Allergens: contains milk and celery (celeriac). See the allergen notes under Nutrition.
Method
- Heat the oven. Heat the oven to 180°C (160°C fan, gas 4). Rub the butter over the inside of a 1.5 litre ovenproof dish, about 25 × 18cm.
- Prepare the celeriac. Cut the top and bottom off the celeriac, sit it flat and cut away the knobbly skin with a sharp knife. Cut it into quarters, then slice it about 3mm thick with a mandoline or a large, sharp knife. You need 750g.
- Warm the cream. Put the cream, milk, garlic, thyme leaves, nutmeg, salt and a good grind of black pepper in a large, wide pan and bring it to a gentle simmer over a medium heat.
- Simmer the celeriac. Add the celeriac slices and stir gently to coat them. Simmer for 5 minutes, turning the slices now and then, until they start to soften. Don't let it boil hard, or the cream may catch on the bottom of the pan.
- Layer. Lift the slices into the dish with a slotted spoon, laying them flat in overlapping layers, then pour over the cream from the pan. Press the top down so the slices are just covered.
- Bake covered. Cover the dish with a sheet of baking paper and bake for 40 minutes.
- Brown the top. Remove the paper, scatter over the Parmesan and bake for 25 minutes more, until the top is golden and bubbling and a knife slides easily through the middle.
- Rest and serve. Leave it to rest for 10 minutes so the cream can settle, then scatter over a few thyme leaves and serve.
What to serve with celeriac dauphinoise
- Sunday roast: roast beef or lamb with our keto gravy, green beans and tenderstem broccoli.
- Christmas dinner: next to the turkey, pigs in blankets and sprouts. The keto Christmas dinner guide has the carbs for each part of the plate.
- Midweek: with a steak, roast chicken thighs or a slice of baked ham and a green salad.
Ways to change your celeriac dauphinoise
- Gruyère top: swap the Parmesan for 50g grated Gruyère for a softer, more melting crust (Gruyère is also usually made with animal rennet).
- Classic, no cheese: leave out the Parmesan for a more traditional dauphinoise, and bake it uncovered for the last 25 minutes until golden.
- Smoky bacon: scatter 100g cooked smoked bacon lardons between the layers.
- Rosemary: use 1 tsp finely chopped fresh rosemary in place of the thyme.
Any of these changes will alter the nutrition figures.
More keto roast dinner ideas
- Gravy: make our keto gravy, thickened without flour, to go with the roast.
- Christmas: plan the whole meal with our keto Christmas dinner guide.
- Another creamy bake: try our keto cottage pie with a cauliflower mash topping.
- Cream explained: read whether double cream is the same as heavy cream, with the carbs in UK creams.
Storage
- Fridge: cool it, cover it and put it in the fridge within 1 to 2 hours, then eat it within 2 days.
- Freezer: once it has cooled, put it in the freezer in portions within 1 to 2 hours and use it within 3 months. The sauce may turn a little grainy. Defrost it in the fridge overnight and eat it within 24 hours.
- Reheating: reheat it only once, covered with foil, at 180°C (160°C fan, gas 4) for 25 to 30 minutes, until it is steaming hot all the way through. Remove the foil for the last 5 minutes to crisp the top.
These times follow the Food Standards Agency's advice on how to chill, freeze and defrost food safely.
Nutrition
Per serving (1/6 of the dish):
| Nutrient | Per serving |
|---|---|
| Energy | 320 kcal |
| Fat | 30.7g |
| of which saturates | 18.9g |
| Carbohydrate | 5.3g |
| of which sugars | 4.3g |
| Net carbs | 5.3g |
| Fibre | 4.7g |
| Protein | 5.7g |
| Salt | 1.18g |
There are no polyols in this recipe, so net carbs are the same as the carbohydrate figure. On UK labels, fibre is already listed separately from carbohydrate, so it isn't subtracted again. Figures are calculated from UK (McCance and Widdowson's CoFID) data for raw celeriac (13-219), double cream (12-334), whole milk (12-596), raw garlic (13-244), fresh thyme (13-893), unsalted butter (17-661), Parmesan (12-526) and salt (17-367). The nutmeg and black pepper aren't counted. Figures will vary with the size of your celeriac and the brands you use.
Allergens: this dish contains milk (cream, milk, butter and Parmesan) and celery, because celeriac is part of the celery allergen group. Parmesan is traditionally made with animal rennet, so check the label if you are cooking for vegetarians. Always check the current labels before cooking for anyone with an allergy.
FAQ
How many carbs are in celeriac?
UK CoFID data gives raw celeriac 2.3g carbohydrate per 100g, against 19.6g for raw old potatoes. Boiled, celeriac has 1.9g and potatoes 17.5g. That is why a serving of this celeriac dauphinoise has 5.3g net carbs, while the same recipe made with 750g of potatoes would have about 26.9g.
Can you make dauphinoise ahead?
Yes. Bake it, let it cool, cover it and put it in the fridge within 1 to 2 hours, then eat it within 2 days. Reheat it once, covered with foil, at 180°C (160°C fan, gas 4) for 25 to 30 minutes, until it is steaming hot all the way through. Uncover it for the last 5 minutes.
Does celeriac taste like potato?
Not exactly. Raw celeriac tastes of celery with a nutty edge, but baking it slowly in garlic and thyme cream mellows it into something mild, savoury and slightly sweet. The texture is close to potato dauphinoise, with soft layers that hold together, though it is less starchy, so the sauce stays a little looser.
Can you freeze celeriac dauphinoise?
Yes, though the cream can turn slightly grainy once it thaws. Cool it, then put it in the freezer in portions within 1 to 2 hours and use it within 3 months. Defrost it in the fridge overnight, eat it within 24 hours and reheat it once until it is steaming hot all the way through.
Is dauphinoise the same as gratin?
Dauphinoise is one kind of gratin. The classic gratin dauphinois from the Dauphiné region of France bakes thin potato slices in cream or milk with garlic, usually without cheese. Many other gratins add cheese or breadcrumbs. Our celeriac version adds a thin Parmesan crust, which you can leave out for a more traditional dish.
How thin should you slice celeriac for dauphinoise?
About 3mm. Thin, even slices cook through at the same speed and stack into neat layers, while thick slices can stay firm in the middle. A mandoline is the quickest way, but always use the hand guard. A large, sharp knife works too: cut the celeriac into quarters first so each piece sits flat.
