Squash Gratin with Mornay Sauce

Squash Gratin with Mornay Sauce is a rich and comforting baked dish that combines tender slices of squash with a creamy, cheesy béchamel sauce. Finished with a golden, bubbling topping, this gratin delivers elegance and heartiness in every bite. It’s the perfect side dish for a holiday meal or a cozy addition to any dinner table.

Why You’ll Love This Recipe

This squash gratin is the ultimate comfort food, offering a delicious balance of creaminess, flavor, and texture. Here’s why it’s a must-make:

• Creamy Mornay sauce adds rich, cheesy depth
• Beautifully layered squash bakes to tender perfection
• Makes an impressive side dish for gatherings or potlucks
• Easy to prepare ahead and bake later
• A delicious way to enjoy seasonal squash

ingredients

(Tip: You’ll find the full list of ingredients and measurements in the recipe card below.)

• Yellow squash or zucchini, thinly sliced
• Butter
• All-purpose flour
• Whole milk
• Gruyère or Swiss cheese, grated
• Parmesan cheese, grated
• Salt
• Black pepper
• Nutmeg (optional)
• Garlic, minced (optional for extra flavor)
• Breadcrumbs or extra cheese for topping (optional)

directions

1. Preheat oven to 375°F (190°C). Grease a medium baking dish with butter or nonstick spray.
2. In a saucepan, melt butter over medium heat. Add flour and whisk continuously for 1–2 minutes to form a roux.
3. Slowly add the milk, whisking to remove lumps. Cook until thickened, about 5 minutes.
4. Stir in Gruyère and half of the Parmesan cheese until melted and smooth. Season with salt, pepper, and a pinch of nutmeg.
5. Layer the sliced squash in the baking dish, overlapping slightly.
6. Pour the Mornay sauce evenly over the squash. Tap the dish gently to help it settle.
7. Sprinkle remaining Parmesan and breadcrumbs (if using) over the top.
8. Bake for 30–35 minutes, or until golden and bubbly. Let rest for 5 minutes before serving.

Servings and timing

Serves 6
Prep time: 15 minutes
Cook time: 35 minutes
Total time: 50 minutes

Variations

• Mixed vegetables: Add thinly sliced potatoes or eggplant for a heartier gratin.
• Different cheeses: Try white cheddar or Fontina for a different cheesy flavor.
• Low-carb version: Use cream instead of milk and almond flour instead of all-purpose flour.
• Herbaceous twist: Add fresh thyme, basil, or chives to the sauce for a flavor boost.
• Spicy: Add a pinch of cayenne or red pepper flakes for heat.

storage/reheating

Store leftovers in an airtight container in the refrigerator for up to 3 days.
Reheat in a 350°F oven until warm and bubbly, about 15–20 minutes.
Microwave reheating works for individual portions but may soften the topping.
Freezing is not recommended due to the high dairy content and squash texture.

FAQs

What is Mornay sauce?

Mornay sauce is a classic French white sauce (béchamel) enriched with cheese, usually Gruyère and Parmesan.

Can I use zucchini instead of yellow squash?

Yes, zucchini works great and can be used alone or in combination with yellow squash.

Should I cook the squash before layering it?

No need. Thinly slicing the squash allows it to cook through perfectly in the oven.

Can I make this gratin ahead of time?

Yes, assemble it up to one day ahead, cover, refrigerate, and bake when ready.

How do I prevent the sauce from curdling?

Cook the sauce gently and stir continuously. Don’t boil once the cheese is added.

What’s the best cheese for Mornay sauce?

Gruyère is classic, but Swiss, Fontina, or even sharp white cheddar work beautifully.

Can I add meat to this dish?

Absolutely. Cooked bacon, ham, or rotisserie chicken make great additions for a main dish version.

What if I don’t have breadcrumbs?

You can top it with crushed crackers, extra Parmesan, or simply skip the topping for a lighter finish.

Is this gluten-free?

Use a gluten-free flour blend for the roux and skip breadcrumbs to make it gluten-free.

Can I use plant-based milk?

Yes, but make sure to choose an unsweetened variety. Note that texture and flavor may vary.

Conclusion

Squash Gratin with Mornay Sauce is a rich and elegant side dish that celebrates the comforting flavors of cheese and tender vegetables. With a crisp golden top and creamy layers beneath, it’s a guaranteed hit for any occasion. Whether you’re cooking for a holiday crowd or elevating a weekday dinner, this gratin delivers warmth, depth, and satisfaction in every bite.

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