Butternut Squash Gratin with Leeks

This Butternut Squash Gratin with Leeks is a cozy, elegant dish that captures the essence of fall and winter dining. Tender slices of butternut squash and sweet, caramelized leeks are layered with creamy cheese sauce and baked until golden and bubbling. It’s the perfect blend of comfort and sophistication, ideal for holiday gatherings, dinner parties, or simply an elevated weeknight side.

Why You’ll Love This Recipe

This gratin combines rich flavor and irresistible texture in every bite. The sweetness of the roasted butternut squash pairs beautifully with the mild onion-like taste of leeks and the creamy, cheesy sauce. It’s comforting yet refined, and it complements everything from roast chicken to beef tenderloin. Plus, it’s vegetarian-friendly and can be made ahead of time for stress-free entertaining.

Time Taken

• Prep Time: 20 minutes
• Cook Time: 45–50 minutes
• Total Time: 1 hour 10 minutes

Grocery List

Produce:

• 1 medium butternut squash (about 2–3 pounds)
• 2 large leeks
• 2 cloves garlic
• Fresh thyme or rosemary (optional for garnish)

Dairy:

• 2 tablespoons unsalted butter
• 1 cup heavy cream
• 1 cup whole milk
• 1 ½ cups shredded Gruyère cheese (or Swiss)
• ½ cup grated Parmesan cheese

Pantry:

• 2 tablespoons all-purpose flour
• Olive oil
• Salt and black pepper
• ¼ teaspoon ground nutmeg (optional)

Ingredients

• 1 medium butternut squash, peeled, seeded, and sliced thinly
• 2 large leeks, white and light green parts only, cleaned and sliced
• 2 tablespoons unsalted butter
• 2 tablespoons olive oil
• 2 tablespoons all-purpose flour
• 1 cup heavy cream
• 1 cup whole milk
• 1 ½ cups shredded Gruyère cheese (or Swiss)
• ½ cup grated Parmesan cheese
• 2 cloves garlic, minced
• Salt and freshly ground black pepper to taste
• ¼ teaspoon ground nutmeg (optional)

Instructions

1. Preheat the Oven:
   Preheat your oven to 375°F (190°C). Lightly grease a baking dish with butter or olive oil.
2. Prepare the Leeks:
   In a skillet over medium heat, add butter and olive oil. Sauté the sliced leeks for 5–7 minutes until they become soft and fragrant. Add garlic and cook for another 1–2 minutes. Remove from heat and set aside.
3. Make the Cream Sauce:
   In the same skillet, add flour and whisk for about a minute to form a roux. Gradually whisk in milk and cream, stirring constantly until smooth and slightly thickened. Season with salt, pepper, and nutmeg. Stir in half of the Gruyère cheese until melted and creamy.
4. Assemble the Gratin:
   Arrange half of the sliced butternut squash in the prepared baking dish. Spread half the leek mixture over it, then drizzle some of the cheese sauce. Repeat with the remaining squash, leeks, and sauce. Top with the remaining Gruyère and Parmesan cheese.
5. Bake:
   Cover the dish with foil and bake for 30 minutes. Remove the foil and continue baking for another 15–20 minutes, or until the top is golden and bubbly.
6. Serve:
   Let the gratin rest for 5–10 minutes before serving. Garnish with fresh thyme or rosemary for a beautiful finish.

Storage Tips

Refrigerate leftovers in an airtight container for up to 3 days. Reheat in a 350°F oven until warmed through. You can also freeze the gratin before baking, assemble it fully, cover tightly, and freeze for up to 2 months. Bake from frozen, adding about 20 minutes to the baking time.

Ingredient Substitutions

• Cheese: Use cheddar, fontina, or mozzarella if you don’t have Gruyère.
• Cream: Substitute with half-and-half or evaporated milk for a lighter option.
• Leeks: Sweet onions or shallots make excellent substitutes.
• Gluten-Free: Use cornstarch instead of flour for the sauce.

Serving Suggestions

Serve this gratin alongside roasted meats like turkey, chicken, or pork tenderloin. It also pairs beautifully with green salads, roasted Brussels sprouts, or crusty bread for a vegetarian main dish.

You Must Know

When preparing leeks, make sure to wash them thoroughly, dirt and grit often hide between the layers. Also, slicing the squash thinly (around ⅛ inch) ensures even cooking and a tender texture.

Chef’s Special Tips

• Use a mandoline slicer for evenly thin squash slices.
• Add a sprinkle of breadcrumbs on top before baking for a crispy golden crust.
• For extra depth, caramelize the leeks for a few more minutes before assembling.
• Let the gratin cool slightly before cutting, this helps it set for cleaner slices.

Cultural and Historical Background

Gratin dishes originated in French cuisine, where “gratin” refers to a baked dish topped with a browned crust, typically made from cheese, breadcrumbs, or butter. This method of cooking became popular in the 17th century and remains a staple in both French and international kitchens.

While the traditional gratin uses potatoes (as in Gratin Dauphinois), variations using seasonal vegetables like butternut squash have become beloved modern adaptations. The pairing of butternut squash and leeks celebrates the natural sweetness and earthy flavors of fall, a nod to both rustic French farmhouse cooking and modern farm-to-table dining.

Conclusion

This Butternut Squash Gratin with Leeks brings a touch of French elegance to your table with minimal effort. It’s rich, creamy, and beautifully golden, the perfect balance of comfort and sophistication. Whether it’s for a family dinner or a festive gathering, this dish is guaranteed to impress. Try it once, and it’ll become a seasonal favorite in your kitchen.

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