Sweet Potato Gratin by Yotam Ottolenghi

This recipe from the Plenty More cookbook is based on a dish from Danielle Postma, a South African chef who worked with Ottolenghi in the UK.

Some years ago, when we stayed a couple of days on an ostrich farm near Swellendam, South Africa, and we had the option to do a “braai” on the patio of our cottages. Yes, please! Our hosts provided the meat (traditional boerewors and ostrich steaks, of course), and we had to grill the meat on the wood fire BBQ ourselves. They also provided a salad and a huge baking tray full of spiced orange-colored mash that was really sweet.

The next day they looked a bit puzzled when we thanked them for the nice and hearty dessert, as it turned out that they hadn’t provided one. It was a spiced sweet potato and pumpkin tray bake that was finished with syrup, so understandably we had interpreted that as a dessert rather than a side dish. You can imagine that surprise for the kids when we told them that they had seconds of sweet potato and pumpkin 😉

This recollection came to mind when I saw the sweet potato recipe in Yotam’s Plenty More cookbook. However, this recipe is actually more like an alternative for the classic potato gratin. And it turned out to be a very nice and super simple side dish: the slight sweetness of the potato works very well with the sage and garlicky cream. The amount of cream is exactly right to seep into the sweet potato yet leave a little bit of reduced sauce at the bottom of the oven dish to spoon over when serving.

In this respect, it should be noted that I prefer “regular” sweet potatoes, those with a light tan skin and a slightly yellow interior. Its flesh is creamy but firm enough to be used for a gratin like this.

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The more commonly available sweet potatoes in the stores here have orange flesh and have a reddish-brownish-orangish skin. Also sometimes referred to as “yams”, they are not of the same botanical family, and these ones are quite a bit sweeter and contain more water and therefore become mushier when cooking.

IMG_0416 I made this dish with both varietals several times (also sometimes switching the sage with rosemary or slicing the sweet potato a bit thinner as depicted above) and I feel the orange-fleshed ones are much better suited to be used in a mash or purée.

The recipe

  • about 1½kg / 3 pounds of sweet potatoes (washed, but not peeled)
  • 5 tbsp roughly chopped sage, plus extra to garnish
  • 6 garlic cloves, crushed
  • 1 tbsp olive oil
  • 2 tsp coarse sea salt
  • ½ tsp freshly ground black pepper
  • 250ml / 1 cup single cream
  1. Preheat the oven to 200℃/390℉.
  2. Cut the sweet potatoes into ½cm/¼” slices and in a large bowl, mix them together with the oil, chopped sage, crushed garlic, salt, and pepper.
  3. Arrange the slices of sweet potato and stand them up tightly in a deep, medium-sized ovenproof dish.
  4. Scrape any remaining bits of garlic and sage from the bowl and put them over the potatoes.
  5. Cover the oven dish with aluminum foil, place in the oven, and roast for 45 minutes. Remove the aluminum foil and pour the cream evenly over the potatoes.
  6. Roast, uncovered, for a further 25 minutes until the cream has thickened and the sweet potatoes are completely soft.
  7. Remove from the oven, garnish with the extra chopped sage and serve immediately.

Recipe accuracy:
The recipe is accurate, easy to follow and serves 4 persons as a side dish. Only some minor tweaks from my side. I added 1 tbsp of olive oil to the bowl of sweet potato slices to have the sage and garlic coat them a bit better. I really toned down on the salt part in step 2, as I thought that 2 tablespoons were way too much to start with. I use 2 teaspoons – at most – and remember that you always have the possibility to season more when the dish is done.

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