The Ultimate Vegetable Au Gratin (Creamy & Cheesy!)

Imagine tender, thinly sliced vegetables—sweet potatoes, zucchini, and eggplant—all cozied up together and baked in a luxuriously rich and creamy three-cheese sauce until bubbling and golden brown. That, my friends, is the comforting, elegant magic of this Vegetable au Gratin. This isn’t just a side dish; it’s a show-stopping centerpiece that celebrates the best of fresh produce. It is, without a doubt, the most irresistible vegetable dish you will ever make.

I promise you, the moment you pull this bubbling, golden-crusted dish from the oven, you will be in awe. Each bite is a perfect harmony of tender vegetables and velvety, cheesy sauce. It’s the kind of side dish that steals the show, perfect for a holiday feast, a special Sunday dinner, or anytime you want to make vegetables feel like a decadent treat.

Get ready to master a classic French technique and create a dish that is the absolute pinnacle of comfort food elegance.

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Why This Will Be Your New Favorite Side Dish!

You are going to be completely smitten with this rich, cheesy, and beautiful gratin. It’s a guaranteed hit. Here’s why you have to try it:

• Incredibly Rich and Flavorful: The homemade three-cheese béchamel sauce is luxuriously creamy and packed with complex, nutty, and savory flavors that perfectly coat every vegetable.
• A Stunning Presentation: The technique of arranging the vegetable slices vertically creates a beautiful, rustic, and impressive-looking dish that’s perfect for entertaining.
• Turns Humble Veggies into a Star: This recipe is the perfect way to elevate everyday vegetables like zucchini, squash, and sweet potatoes into a truly decadent and crave-worthy dish.
• Surprisingly Simple to Make: While it looks and tastes gourmet, the process is straightforward—slicing veggies and whisking a simple cheese sauce is all it takes!
• The Ultimate Comfort Food: There is nothing more comforting than a bubbling, cheesy, baked casserole hot from the oven. This dish is a warm hug on a plate.

Recipe Snapshot

Your Shopping List for This Cheesy Masterpiece

This recipe uses a beautiful mix of fresh vegetables and classic cheeses. Here’s what you’ll need:

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→ For the Vegetables

• 2 large yellow squash & 2 large zucchini → Classic summer squash that become wonderfully tender.
• 2 sweet potatoes → Or Yukon Gold potatoes. They add a lovely sweetness and hearty texture.
• 2 medium eggplants → Adds a creamy, earthy element.
• 1 small red onion → For a touch of aromatic sweetness.
• 1 tablespoon olive oil → To coat the vegetables.
• ½ tablespoon dried basil, ½ tbsp salt, ½ tbsp black pepper → For seasoning the vegetables before baking.

→ For the Rich Cheese Sauce

• 3 tablespoons butter & 3 tbsp all-purpose flour → The base of our classic roux for the béchamel.
• 2 cups whole milk → For a rich and creamy sauce. 2% milk also works.
• 1 cup shredded fontina cheese → A fantastic melting cheese with a mild, nutty flavor.
• ½ cup shredded Gruyere cheese → The secret weapon for a deep, nutty, and complex flavor.
• ½ cup shredded Parmigiano cheese → For a sharp, salty bite.
• Fresh thyme, rosemary, or parsley → For a fresh, aromatic garnish.

Let’s Get Cooking! Your Step-by-Step Guide

Ready to create the most luxurious vegetable dish of your life? Let’s break it down into simple, manageable steps.

Part 1: Prep and First Bake the Vegetables

1. Preheat and Prep: Preheat your oven to 375°F (190°C).
2. Slice the Vegetables: Using a sharp knife or a mandolin for speed and precision, thinly slice the zucchini, yellow squash, eggplant, sweet potatoes, and red onion to about 1/4-inch thickness. Uniform slices are key for even cooking!
3. Season the Veggies: In a very large bowl, toss all the sliced vegetables with the olive oil, dried basil, 1/2 tablespoon of salt, and 1/2 tablespoon of black pepper. Use your hands to make sure every slice is lightly coated.
4. Arrange the Vegetables: In a large oven-safe skillet or a casserole dish, begin arranging the vegetable slices vertically. Pack them tightly together, side by side, creating a beautiful layered pattern.
5. First Bake: Place the dish in the preheated oven and bake for 25 minutes. This gives the vegetables a head start to become tender.

Part 2: Make the Sauce and Final Bake

6. Make the Béchamel: While the vegetables are baking, melt the butter in a saucepan over medium heat. Whisk in the flour and cook, stirring constantly, for 1-2 minutes to form a roux.
7. Add Milk and Thicken: Gradually pour in the milk, whisking continuously to prevent any lumps. Continue to cook and whisk until the sauce is smooth and has thickened enough to coat the back of a spoon. Stir in 1/2 teaspoon of salt.
8. Melt in the Cheeses: Remove the sauce from the heat and stir in the shredded fontina, Gruyere, and Parmigiano cheeses. Keep stirring until the cheeses are completely melted and the sauce is velvety smooth.
9. Combine and Finish Baking: After 25 minutes, carefully remove the vegetables from the oven. Pour the glorious cheese sauce evenly all over the top. Sprinkle a little extra cheese over the surface for that perfect golden crust.
10. Final Bake: Return the dish to the oven and bake for an additional 20-25 minutes, until the top is bubbly and beautifully golden brown.
11. Rest and Garnish: Let the gratin rest for a few minutes before serving. Garnish with a sprinkle of fresh herbs and enjoy!

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Creamy Vegetable Au Gratin

This irresistible Vegetable au Gratin features layers of tender squash, sweet potatoes, and eggplant baked in a rich, creamy three-cheese sauce with fontina, Gruyere, and Parmigiano. The ultimate elegant and comforting side dish!

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Prep Time 15 minutes mins

Cook Time 1 hour hr

Total Time 1 hour hr 15 minutes mins

Servings: 8

Course: Side Dish

Cuisine: American, French

Calories: 334

Ingredients Equipment Method Notes

Ingredients

  

For the Vegetables

• 2 large yellow squash, sliced
• 2 large zucchini, sliced
• 2 sweet potatoes, or Yukon Gold potatoes, sliced
• 2 medium eggplants, sliced
• 1 tablespoon olive oil
• 1/2 tablespoon dried basil
• 1/2 tablespoon salt
• 1/2 tablespoon black pepper
• 1 small red onion, sliced

For the Cheese Sauce

• 3 tablespoons butter
• 3 tablespoons all-purpose flour
• 1/2 teaspoon salt
• 2 cups whole milk can use 2%
• 1 cup shredded fontina cheese more for topping
• 1/2 cup shredded Gruyere cheese or mild white cheddar, more for topping
• 1/2 cup shredded Parmigiano cheese more for topping
• as needed Fresh thyme, rosemary, or fresh parsley for garnish

Equipment

• Mandolin or sharp knife
• Large Bowl
• Large oven-safe skillet or casserole dish
• Saucepan
• Whisk

Method

 

Part 1: Prep and First Bake

1. Preheat your oven to 375°F (190°C). Thinly slice all vegetables to about 1/4-inch thick.
2. In a large bowl, toss the sliced vegetables with olive oil, dried basil, 1/2 tablespoon of salt, and 1/2 tablespoon of black pepper.
3. Arrange the vegetables vertically in a large skillet or casserole dish, packing the slices tightly together.
4. Bake the vegetables in the preheated oven for 25 minutes.

Part 2: Make Sauce and Final Bake

1. While vegetables bake, melt the butter in a saucepan over medium heat. Add the flour and cook, stirring constantly, for 1-2 minutes to form a roux.
2. Gradually add the milk, whisking continuously until smooth and thickened. Stir in 1/2 teaspoon of salt.
3. Remove from heat and stir in the shredded fontina, Gruyere, and Parmigiano cheeses until completely melted and smooth.
4. After 25 minutes, remove vegetables from the oven. Pour the cheese sauce evenly over the vegetables. Sprinkle with additional cheese.
5. Return to the oven and bake for an additional 20-25 minutes, or until the top is golden brown and bubbly.
6. Let it rest for a few minutes. Garnish with fresh herbs and serve warm.

Notes

Even Slicing: Using a mandolin is highly recommended for slicing the vegetables evenly, which ensures they all cook at the same rate.

Cheese Quality: For the best, smoothest, and most flavorful sauce, buy blocks of cheese and shred them yourself.

Let it Rest: Allowing the gratin to rest for 5-10 minutes before serving is essential to help the sauce set.

Nutrition Disclaimer: Nutrition information is automatically calculated, so should only be used as an approximation.

WiseRecipes’ Top Tips for Gratin Perfection

These simple tricks will ensure your vegetable au gratin is absolutely flawless.

1. Even Slicing is Crucial. This is the most important step for texture. A mandolin is your best friend here, as it creates perfectly uniform slices in a fraction of the time. This ensures all the different vegetables cook evenly and are tender at the same time.
2. Pack the Vegetables Tightly. When arranging the slices vertically, don’t be afraid to really pack them in there. This helps them hold their shape and ensures that every bite has a perfect ratio of vegetable to sauce.
3. Shred Your Own Cheese. For the smoothest, meltiest cheese sauce, always buy blocks of cheese and shred them yourself. Pre-shredded cheeses are coated in anti-caking agents that can make your sauce gritty.
4. Don’t Stop Whisking the Sauce. When making the béchamel, continuous whisking is key, especially when you first add the milk. This is the secret to a perfectly smooth, lump-free sauce.
5. Let It Rest Before Serving. I know it’s tempting to dive right into that bubbling, cheesy masterpiece, but letting the gratin rest for 5-10 minutes is essential. This allows the sauce to set up slightly, so it doesn’t run everywhere when you serve it.

Keep It Fresh! Storing Your Leftovers

This gratin makes for incredible leftovers, as the flavors continue to meld together.

• Refrigerator: Once cooled, cover the dish tightly with foil or transfer leftovers to an airtight container. It will keep well in the refrigerator for up to 4 days.
• Reheating: For best results, reheat the gratin in a 350°F oven for 15-20 minutes, or until warmed through and bubbly. This will help re-crisp the cheesy topping. You can use a microwave, but the texture won’t be as good.

FAQs: Your Vegetable Gratin Questions, Answered!

Do I have to use all these different vegetables?

Not at all! This recipe is very flexible. You can use any combination of sturdy, sliceable vegetables. Regular potatoes, butternut squash, bell peppers, or fennel would all be delicious. Just aim for a similar total quantity.

Can I use different cheeses?

Of course! The combination of fontina, Gruyere, and Parmigiano is classic for its flavor and melting properties, but feel free to experiment. Mild white cheddar, provolone, or Gouda would all be excellent substitutes for the fontina or Gruyere.

Can I prepare this dish ahead of time?

Yes, you can assemble the entire gratin (through step 9) up to a day in advance. Cover it tightly and refrigerate. When you’re ready to bake, you may need to add an extra 10-15 minutes to the total baking time since you’re starting from cold.

How do I prevent my sauce from being lumpy?

The key is to add the milk gradually and whisk constantly. Start by adding just a splash of the milk to the roux (the butter/flour mixture) and whisk vigorously to form a smooth, thick paste. Then, continue to slowly stream in the rest of the milk while whisking, and you’ll have a perfectly smooth sauce.

Final Thoughts: The Ultimate Veggie Indulgence

There is something truly special about a dish that transforms simple, everyday ingredients into something so extraordinarily delicious and beautiful. This Vegetable au Gratin is a celebration of comfort, elegance, and the magic of a perfect cheese sauce. It’s a rewarding and deeply satisfying dish that I know will become a treasured favorite in your home. Happy cooking!