The Best Low-Carb "Potato" Gratin

Martina SlajerovaUpdated 29 September 2023★★★★★4.6 (312 ratings)

Ready in 2h 30m
10.4 g net carbs
445 kcal
Serves 8

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Potato Gratin, also known as Potato Dauphinoise is one of the meals I didn't want to give up when I started following a low-carb diet. When looking for a keto alternative, I spent quite some time trying to figure out what works best instead of potatoes.

Cauliflower was the first substitute I tried but wasn't happy with the result. There is a better ingredient for making low-carb potato gratin - rutabaga, also known as swede. Although rutabaga contains more carbs than cauliflower, in my opinion it's worth using it in this recipe.

I've been using this amazing low-carb vegetable for years - mostly in soups and stews like this one. It has proven to work even for keto fries and makes the best potato salad - a traditional Czech Christmas side dish that is served with breadcrumbed fried fish.

You could try other vegetables too - kohlrabi or turnips are also good options. Just for a comparison (per 100 grams/ 3.5 ounces):

white potatoes - 13.3 g net carbs (15.7 g total carbs)
sweet potatoes - 17.2 g net carbs (20.3 g total carbs)
turnips - 4.6 g net carbs (6.4 g total carbs)
rutabaga / swede - 6.3 g net carbs (8.6 g total carbs)
cauliflower - 3 g net carbs (5 g total carbs)
kohlrabi - 2.6 g net carbs (6.2 g total carbs)
celery root - 7 g net carbs (9 g total carbs)
radishes - 1.8 g net carbs (3.4 g total carbs)
daikon radish - 4 g net carbs (6 g total carbs)
parsley roots - 1.7 g net carbs (3.5 g total carbs)

Since it's the Holiday season, make sure you check out my festive keto recipes!

Step-by-step

(Note: This recipe is best prepared a day in advance as it will have time to soak up any excess juices.) Preheat the oven to 160 °C/ 320 °F (fan assisted), or 180 °C/ 355 °F (conventional). Peel and slice the onion and place in a hot pan greased with ghee. Cook over a medium heat until fragrant for about 5 minutes while stirring.
Slice the bacon and add to the pan with the onion. Add thyme and cook until the bacon is lightly browned from all sides. Take off the heat and set aside.
Meanwhile, peel and halve the rutabaga. Cut thinly, into about ¹/₄ cm (¹/₈ inch) slices. (Note: If you want to reduce the baking time to just 45-50 minutes, pre-cook the rutabaga. Place in a pot filled with water and cook for about 10 minutes. Then, drain and use as described in the following steps but with only 1 cup of the stock instead of 3 cups. Remove the baking foil and top with creme fraiche and Parmesan cheese for the last 20 minutes of the cooking process.)
There will be three layers of rutabaga. Place the first layer of slices into a large baking dish greased with some ghee. Top with half of the bacon and onion mixture.
Add half of the grated cheddar cheese. Top with another layer of rutabaga slices, bacon, onion and grated cheddar. Finally, top with the last layer of rutabaga slices. In a bowl, combine the cream, chicken stock, salt and pepper.
Pour into the baking dish over the rutabaga until almost covered. If needed, add some more chicken stock. Season with more salt and pepper to taste.
You can use one large baking dish or a single-serving baking dish like this one from Le Creuset.
Cover with aluminum foil and transfer into the oven over a baking dish to collect any juices dripping from the aluminum cover. Bake covered for an hour.
After an hour, the rutabaga will get softer. Remove the aluminum foil and press the rutabaga down with a spatula to submerge it into the cream mixture and prevent it from drying. Bake for another 45-60 minutes or until the rutabaga gets tender, pressing it down with a spatula every 15 minutes. When done, remove from the oven and set aside. Turn the oven up to 200 °C/ 400 °F (fan assisted), or 220 °C/ 425 °F (conventional).
Spread the creme fraiche and grated parmesan cheese on top.
Place back in the oven for another 20-30 minutes or until the cheese is melted and the top is crispy and golden brown.
I baked mine a day ahead, let it chill and stored in the fridge to set. Then I made the final browning just before serving. This way if wasn't burning hot, was perfectly set and ready to be served straight from the oven.
Serve as a side with meat or fish, or as a light lunch - by itself with some crispy greens. It tastes great both hot and cold.
Store in the fridge for up to 5 days. Enjoy!

Recipe