Parsnip and Sweet Potato Gratin

The ultimate comfort food recipe, Parsnip and Sweet Potato Gratin. Get cooking this cheesy side dish to serve with your Sunday roast or Christmas dinner.

Root Vegetables cooked in a creamy mustard sauce with spinach then baked in the oven with a sprinkle of cheese.

How to make Parsnip and Sweet Potato Gratin?

Make this delicious Gratin at home following tips on this blog page, check out the slideshow video to see how simple it is.

Easy to follow step by steps are given in the printable recipe card

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Find out more about the history of Gratin from wiki.

How thick to cut Parsnips and Sweet Potatoes?

Peel and slice parsnips and sweet potato into similar thickness slices. They should be about 1cm thick.

Should I parboil the parsnip and sweet potato?

You do not need to parboil the sweet potato and parsnips in water. This will make the gratin too watery.

The benefit of cooking the parsnip and sweet potato in with the dairy is the sauce will naturally thicken with the release of starch from the sweet potato.

Instead, lightly boil the vegetables in cream, milk and add wholegrain mustard, thyme and salt & pepper for extra flavour.

Should I boil cream for Gratin?

Do not turn the hob too high when boiling the vegetables in the gratin cream sauce, it should be a gentle boil, not ferocious boil.

After 15 minutes the parsnips and sweet potatoes will have softened enough.

Stir the spinach through once the potato and parsnip has softened.

How to layer Parsnip & Sweet Potato?

No need to spend unnecessary time layering the parsnip & sweet potato slices. Just pour it all in they will naturally fall into layers.

I usually pull the biggest slices to the top before adding cheese on top though!

What dish to cook Gratin in?

Use an oven-safe casserole dish, it does not need a lid. We actually used a pie dish as it fit perfectly!

What cheese to put on top of a Gratin?

We used mozzarella cheese so that the kids would enjoy it too, but a mature cheddar or Parmesan will give a richer taste. Gruyere cheese is also a great choice.

Sprinkle over with as much cheese as you wish!

What temperature and how long to cook Root Vegetable Gratin?

Bake on the middle shelf at 160C/320F fan oven for 30 minutes.

How to serve Parsnip and Sweet Potato Gratin?

Perfect side dish to many recipes especially comfort foods, like Roast Dinners.

You can serve straight from the oven as seen in the below picture with the stringy melted cheese.

If you wanted neater slices of Gratin you need to allow it time to cool so the cheese and and cream sauce can firm up.

Can I make Gratin ahead of time?

Yes, you can make Gratin ahead of time which is perfect when you need the oven to cook joints of meat etc.

How long does Gratin keep in fridge?

Cook ahead allow to cool and keep covered in refrigerator for upto 3 days.

The best thing about making Parsnip and Sweet Potato Gratin ahead of time is you can cut neater slices once it has cooled down and firmed up!

How to reheat leftover slices of Gratin in microwave?

Cut the desired amount and reheat on a microwaveable plate in the microwave until hot usually about 2-4 minutes (time varies on the size of slice and microwave wattage)

How to reheat whole Parsnip and Sweet Potato Gratin which has been made ahead?

Reheat the whole Gratin at 160c/320f fan oven, until hot through, should take about 30 minutes.

Seen here served with our Braising Steak with Horseradish Gravy. and Yorkshire Pudding.

📖 Step by Step Recipe

Check out some of our Roasts below for inspiration of what to serve the Parsnip & Sweet Potato Gratin with?

What other vegetables can be used for Gratin?

You can choose any root, squash or potato you like.

We are big lovers of parsnips and they pair nicely with sweet potatoes so that's why we chose this. But feel free to mix it up!

We hope you enjoyed this Parsnip and Sweet Potato Gratin recipe as much as we do.

Please leave us a comment/rating below.