This creamy sweet potato gratin is ultra luxurious, with buttered leeks and a hint of smoked paprika. Perfect for a special occasion!
Have you ever cooked something that barely even makes it to the dinner table, because you just can't stop nibbling it straight from the dish? That was me with this creamy sweet potato gratin. It. Is. Incredible.
What is a gratin?
A gratin (pronounced gra-tan) is any type of bake that's cooked in a shallow dish, topped with some sort of crispy topping, such as breadcrumbs or cheese.
You can 'gratinate' pretty much anything, but potatoes are one of the most common ingredients to find in a gratin.
Potato gratin has all sorts of names, depending on the exact cooking method, and whereabouts in the world you are:
- scalloped potatoes
- potatoes au gratin
- funeral potatoes
- gratin dauphinois
- dauphinois potatoes
- potato bake
Whatever you call it, the end result is pretty much the same: creamy potatoes, baked in the oven with a crispy topping.
And it is wonderful.
Sweet potato gratin
I'll admit, sweet potato isn't usually my favourite vegetable. I'll take a regular French fry over a sweet potato one any day of the week.
But this sweet potato gratin... wow. It's definitely converted me to the wonders of sweet potato.
Thin slices of sweet potato are baked in a creamy, cheesy sauce - with garlicky buttered leeks, just because. The potato absorbs the sauce and becomes soft and creamy, and I also added my favourite spice of all time, smoked paprika, which brings some depth. The flavour is just incredible.
The finished dish doesn't feel overly sweet, as the flavour of the sweet potato is perfectly balanced by the salty cheese, as well as the smokiness of the paprika.
How to make sweet potato gratin
Step 1: Make the buttered leeks
The recipe begins by sautéing some leeks with butter and garlic. I wanted to add something extra to the sweet potato bake, but still wanted the potatoes to be the stars of the show, so these leeks are perfect.
They bring heaps of flavour to the dish, without taking over completely.
Just cook them over a medium heat for about 5-10 minutes, until they're beautifully soft, but not too browned.
Step 2: Thinly slice sweet potato
Peel your sweet potato, and cut it into nice thin slices.
You could use a mandoline if you have one (using its thickest setting - we don't quite want paper thin here), but I actually sliced mine by hand. It didn't take long, and it was quite easy to cut slices that were only 2 or 3 millimetres thick.
Step 3: Begin layering
The sweet potato bake is constructed by layering up the slices of sweet potato with the buttered leeks and some grated parmesan cheese (a vegetarian version, of course!).
To help the sweet potato cook, don't overlap them too much - lay them out in single layers, with just a small amount of leeks and cheese. This way, you end up with lots of thin layers, with a little bit of cream in between each layer to cook the potato.
I seem to be a fan of layered dishes lately - there was a similar layering process in my cheesy eggplant bake, which was equally spectacular. Layering something with cheese is never a bad idea.
Step 4: Pour over the cream sauce
The sauce for this sweet potato gratin is simply cream, salt and pepper, dried thyme, and smoked paprika. The paprika really does bring something special to the dish, so I'd recommend not skipping it.
You only need a small drizzle of cream in between each layer of potato - it doesn't need to be drenched.
Carry on layering until you've used all the ingredients.
Step 5: Bake
Cover the dish (I used a baking dish that had a lid, but you could use kitchen foil if you don't have a lid), and pop it in the oven.
It does take a while to bake, as the sweet potato needs time to soften up in the cream. But believe me - it's worth the wait.
The end result is irresistibly creamy with the salty cheese coming through in every bite. And the crispy bit on top is just the icing on the cake.
How to serve sweet potato gratin
There's no denying that this sweet potato gratin is a decadent dish. I certainly wouldn't cook something this rich on a daily basis, and a fairly small portion goes a long way.
So personally, I'd save this dish for a special occasion - it would make your Thanksgiving or Christmas dinner absolutely unforgettable, for example.
Or, cook it as part of a family lunch on a cosy Sunday, alongside some plainer vegetable side dishes.
Can you use regular potatoes instead?
If you're not a sweet potato fan, you can swap them out for regular potatoes. I'd actually recommend giving the sweet potatoes a try, as the hint of sweetness is absolutely incredible in the finished dish, even if it's not usually your thing.
But if regular potatoes are all you have on hand, you can use them instead.
Generally, regular potatoes take a little longer to cook than sweet potatoes, so it may need a bit more time in the oven. Make sure you slice your potatoes super thin, to help them along, and cover the dish tightly so the topping doesn't burn while it's baking.
Alternatively, you could boil the sliced potatoes for a few minutes before layering your dish, just to give them a head start.
Can I prepare this sweet potato bake in advance?
Absolutely! Just layer everything up, and leave it in the fridge until you're ready to bake.
📖 Printable Recipe
Creamy Sweet Potato Gratin
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- 1 tablespoon butter
- 1 large leek, quartered lengthwise then sliced
- 3 cloves garlic, minced
- 600 g (~ 1 ⅓ lb) sweet potato (1 large or 2 small)
- 500 ml (~ 2 cups) single cream
- 1 teaspoon smoked paprika
- 1 teaspoon salt
- 1 teaspoon black pepper
- 1 teaspoon dried thyme
- 100 g (~ 3 ½ oz) vegetarian parmesan-style cheese, finely grated
- Melt the butter in a frying pan, and add the sliced leek and minced garlic. Cook over a medium-low heat for 5-10 minutes, until the leek is very soft but not overly browned.
- Peel the sweet potato, and cut it into thin slices (ideally 2-3mm).
- Transfer the cream into a jug, and add the smoked paprika, salt and pepper, and dried thyme. Mix thoroughly to combine.
- Pour about a tablespoon of the cream mixture into the bottom of a baking dish (mine measured approximately 8 x 8 inches), and spread it around. This helps to stop the potato sticking to the bottom of the dish.
- Now begin layering your ingredients. Add a single layer of sweet potato slices, scatter a few buttered leeks on top, and a light sprinkling of finely grated parmesan. Drizzle over a little more of the cream mixture. Repeat these layers until you've used all of the ingredients. Finish the dish by pouring any remaining cream on top, and scattering over any remaining cheese.
- Add a lid to the dish, or cover tightly with some kitchen foil. Bake at 190°C (Gas Mark 5 / 375°F) until the sweet potato is soft, and offers no resistance when you insert a sharp knife. My bake took about 1 hour 25 minutes, but the exact time will depend on exactly how thinly you sliced your potatoes.
Nutritional information is approximate, and will depend on your exact ingredients. Please calculate your own nutritional values if you require accuracy for health reasons.