This Butternut Squash and Potato Gratin is the perfect simple side dish for any meal, whether it’s a holiday or weeknight dinner.
Thin slices of butternut squash and potatoes are tossed with cheese, a creamy white sauce infused with leeks and thyme, and baked until bubbling and golden brown.
Ordinary ingredients become extraordinary when combined in this casserole. If you thought au gratin potatoes required special cooking techniques or hours in the kitchen, let us take you through the easy step by step process for making this classic dish.
The Difference Between Scalloped and Au Gratin Potatoes
Scalloped potatoes consist of thinly sliced potato layers baked with heavy cream and/or milk.
Potatoes Au Gratin also consist of thinly sliced potato layers baked in a cream sauce, but with the addition of cheese and sometimes breadcrumbs sprinkled on top.
However, there are countless recipes for scalloped potatoes that call for cheese or breadcrumbs, or both. But the classic definition for scalloped potatoes does not include cheese. Confusing, huh? Well, regardless of what they are called, we do know one thing…they are seriously comforting and delicious and we’ll take a serving of either!
Russets or Yukon Golds?
They are both winners. Russets have the most starch which makes the creamiest sauce, but Yukons are waxy potatoes and tend to hold their shape a little better.
We’re using a combination of russets and butternut squash. We love the slightly sweet addition of the butternut squash. It’s the perfect pairing.
Butternut Squash and Potatoes Au Gratin Are Easier to Make Than You Think!
- Prepare the cream sauce. This is a basic white sauce of dairy-free, soy-free margarine, leeks, garlic, garbanzo bean (a.k.a. chickpea) flour, rice milk, a bay leaf, and fresh thyme.
- Cut the butternut squash and potatoes into 1/8-inch slices for even cooking. We highly suggest using a mandolin for slicing. It is possible to cut by hand, but the slices may be uneven and the task will take so much longer. If you don’t have a mandolin, check out this simple, value conscious mandolin that will save tons of time.
Prep Squash Like a Pro
- Lay the squash on its side. Using a large, sharp chef’s knife, trim the top and bottom, then cut crosswise through the middle.
- Peel the skin using a peeler or Chef’s knife.
- Stand each section on its flat side and cut in half lengthwise. Using a melon baller or a large spoon, scrape out seeds and any pulp or stringy bits. Place each half cut side down and slice lengthwise in half again. Cut 1-pound of the squash into 1/8-inch slices.
- In a large bowl, add potatoes, squash, cream sauce, and cheddar shreds. Gently toss well to combine.
- Transfer to a lightly greased 13×9-inch baking dish. Cover tightly with foil. This will help cook the potatoes as they steam and boil in the sauce. Bake for 45 minutes. Remove the foil and sprinkle with a crumb topping or just a little more cheese. Bake, uncovered for another 25-30 minutes, until vegetables are tender.
- If your top layer doesn’t brown as much as you’d like, crank up the broiler and broil for a couple of minutes until the top is golden.
Butternut Squash and Potatoes Au Gratin will go with just about any main dish that you can imagine!
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Butternut Squash and Potatoes Au Gratin
Yield 12 Servings
Free of: gluten and top 8 allergens.
Ordinary ingredients become extraordinary when combined in this casserole!
4 tbsp dairy-free, soy-free margarine, such as Earth Balance buttery sticks
2 cups leeks, washed well and thinly sliced, white and pale green parts only
3/4 tsp sea salt, divided (1/4 tsp + 1/2 tsp)
2 tsp minced garlic
1/3 cup garbanzo bean flour
4 cups unsweetened rice milk
1 bay leaf
1 tsp chopped fresh thyme
1/8 tsp white pepper
1/8 tsp ground nutmeg
2 pounds russet potatoes, peeled and sliced 1/8-inch thick (see recipe notes)
1 pound butternut squash, peeled, seeded, quartered and sliced 1/8-inch thick (see recipe notes)
2-1/2 cups cheddar-style shreds, such as Daiya, divided (2 cups + 1/2 cup)
1/4 cup gluten-free breadcrumbs or panko, optional
1/2 tsp smoked paprika, optional
- For cream sauce, in a medium saucepan, melt margarine over medium heat. Add the leeks and 1/4 teaspoon salt and cook for about 8 minutes until very soft, stirring occasionally. Add garlic and cook for another 30 seconds.
- Add flour and cook for 1 minute, stirring constantly. Gradually whisk in milk. Add bay leaf and thyme and increase heat to medium-high. When sauce comes to a simmer, lower heat to medium-low and gently simmer for 15 minutes, stirring occasionally. Remove from heat. Whisk in remaining 1/2 teaspoon salt, pepper, and nutmeg. Remove and discard bay leaf. Set sauce aside.
- Preheat oven to 400° F.
- To assemble, in a large bowl, add potatoes, squash, reserved cream sauce, and 2 cups cheddar-style shreds. Gently toss well to combine. Transfer to a lightly greased 13x9-inch baking dish. With fingers separate and arrange butternut squash and potatoes so they are mixed fairly evenly. Cover tightly with foil sprayed with cooking spray. Bake for 45 minutes.
- While casserole is baking, in a small bowl, mix the remaining 1/2 cup cheddar shreds, bread crumbs, and smoked paprika.
- Remove foil and sprinkle bread crumb mixture over the casserole. If you choose to omit the crumb topping, sprinkle with remaining half cup of cheddar-style shreds, omitting the breadcrumbs and paprika. Continue to bake, uncovered until vegetables are tender, about 25-30 additional minutes.
- Let rest for 15 minutes before serving.
- Make the sauce before slicing the potatoes and squash. This way you will not have to place the potatoes in water which will release the starches needed for a creamy casserole.
- Cut the butternut squash and potatoes into 1/8-inch slices for even cooking. We highly suggest using a mandolin for slicing. It is possible to cut by hand, but the slices may be uneven and the task will take so much longer.
- To prep squash like a pro, lay the squash on its side. Using a large, sharp chef's knife, trim the top and bottom, then cut crosswise through the middle. Peel the skin. Stand each section on its flat side and cut in half lengthwise. Using a melon baller or a large spoon, scrape out the seeds and any pulp or stringy bits. Place each half cut side down and slice lengthwise in half again. Cut 1-pound of the squash into 1/8-inch slices.
- We have slightly modified this recipe that we first developed for Allergic Living Magazine.
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