Layered Sweet Potato & Squash Casserole

This Layered Sweet Potato & Squash Casserole is a beautiful, comforting side dish made with thinly sliced sweet potatoes and tender winter squash layered with butter, herbs, and a creamy, cheesy sauce. The sweet vegetables become wonderfully tender while the top turns golden and slightly crisp.Servings: 6–8
Prep time: 25 minutes
Bake time: 50–60 minutes
Total time: About 1 hour 25 minutes

🛒 Ingredients

For the vegetable layers

• 2 large sweet potatoes, peeled
• 1 medium butternut squash, peeled and seeded
• 1 small yellow onion, thinly sliced
• 2 tbsp olive oil
• 2 tbsp unsalted butter, melted
• 2 cloves garlic, finely minced
• 1 tsp fresh thyme leaves or ½ tsp dried thyme
• ½ tsp dried rosemary
• ½ tsp salt
• ¼ tsp black pepper
• ¼ tsp nutmeg

For the creamy sauce

• 1 cup (240 ml) heavy cream
• ½ cup (120 ml) whole milk
• ½ cup (50 g) grated Parmesan
• ½ cup (55 g) shredded Gruyère or sharp cheddar

For the topping

• ½ cup (55 g) shredded Gruyère or cheddar
• 2 tbsp grated Parmesan
• 2 tbsp breadcrumbs (optional)
• Fresh thyme or parsley, for garnish

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👩‍🍳 Instructions

1. Prepare the oven and baking dish

Preheat your oven to 375°F (190°C).

Grease a 9 × 13-inch (23 × 33 cm) baking dish with a little butter or olive oil.

2. Prepare the sweet potatoes and squash

Peel the sweet potatoes and butternut squash.

Cut both into very thin, even slices, approximately ⅛ inch (3 mm) thick.

A mandoline slicer makes this much easier, but a sharp knife works too.

Try to keep the slices similar in thickness so everything cooks evenly.

3. Make the seasoned butter

In a small bowl, combine:

• Melted butter
• Olive oil
• Minced garlic
• Thyme
• Rosemary
• Salt
• Black pepper
• Nutmeg

Mix well.

4. Make the cream mixture

In another bowl, whisk together the heavy cream, milk, Parmesan, and ½ cup of the shredded Gruyère or cheddar.

Set aside.

5. Start layering

Arrange a layer of sweet potato slices across the bottom of the prepared baking dish.

Slightly overlap the slices so there aren’t large gaps.

Add a few pieces of thinly sliced onion.

Brush or drizzle with a little of the seasoned butter mixture.

6. Add the squash

Create the next layer with the sliced butternut squash.

Again, overlap the slices slightly.

Add some onion and another drizzle of the seasoned butter.

7. Continue layering

Repeat the layers:

Sweet potato → onion → seasoned butter → squash → onion → seasoned butter

Continue until all the vegetables are used.

Try to finish with a neat layer of sweet potato and squash arranged in overlapping rows.

8. Add the cream sauce

Slowly pour the cream mixture over the vegetables.

Tilt the baking dish slightly from side to side so the sauce can work its way between the layers.

Don’t worry if the sauce doesn’t completely cover the top—the vegetables will release additional moisture as they bake.

9. Cover and bake

Cover the dish tightly with aluminum foil.

Bake at 375°F (190°C) for 35–40 minutes.

The foil traps steam and helps the vegetables become tender.

10. Add the cheesy topping

Remove the foil.

Sprinkle the top evenly with the remaining shredded cheese and Parmesan.

If you’d like a crunchy topping, sprinkle over the breadcrumbs.

11. Finish baking

Return the uncovered casserole to the oven.

Bake for another 15–20 minutes, until:

• The vegetables are completely tender.
• The cheese is melted.
• The top is golden brown.
• The edges are bubbling.

For an especially golden top, switch to the broiler for 1–2 minutes at the end.

Watch it closely because the cheese can burn quickly.

12. Rest before serving

Remove the casserole from the oven and let it rest for 10–15 minutes.

This allows the creamy sauce to settle and makes the layers easier to serve.

Garnish with fresh thyme or parsley.

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⭐ Tips for Perfect Layers

Slice everything evenly. Thin, uniform slices are the key to tender vegetables that finish cooking at the same time.

Don’t rush the covered baking stage. The steam is what helps soften the sweet potatoes and squash.

Use a sharp cheese. Gruyère, Parmesan, or sharp cheddar balances the natural sweetness of the vegetables beautifully.

Let it rest. Cutting into the casserole immediately can make the sauce run everywhere. A short resting period gives you much neater portions.

🍁 Delicious Variations

Maple Herb

Add 1 tbsp maple syrup to the butter mixture and use extra fresh thyme.

Bacon & Cheddar

Add cooked, crumbled bacon between the vegetable layers and use sharp cheddar.

Sage Brown Butter

Replace the melted butter with browned butter and add 1 tsp finely chopped fresh sage.

Cranberry & Pecan

Add a small handful of dried cranberries and chopped toasted pecans between a couple of the layers for a festive version.

Vegan

Use olive oil instead of butter, plant-based cream, and your favorite dairy-free shredded cheese.

🥄 Make-Ahead

You can assemble the casserole up to 1 day ahead.

Cover tightly and refrigerate.

When ready to bake, allow the dish to sit at room temperature for about 20–30 minutes, then bake as directed. Because the vegetables are cold, you may need an additional 5–10 minutes of covered baking time.

🍠 Serving suggestion

This casserole is especially good alongside roast chicken, turkey, pork, or glazed ham. The creamy, savory cheese sauce balances the natural sweetness of the sweet potatoes and squash beautifully.