Cheesy Baked Zucchini Gratin

This recipe for Cheesy Baked Zucchini Gratin features summer squash and onions in a creamy sauce topped with crispy, buttery breadcrumbs. It tastes light and rich at the same time with a delicate, mouthwatering flavor and can be on your table in under an hour.

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I've never met a gratin I didn't love. From the classic Potato Gratin to a more unique Celery Root and Parsnip Gratin to this Cheesy Baked Zucchini Gratin, there's something about soft veggies in a luxurious cheesy cream sauce topped with a crunchy top that I just can't seem to get enough of.

Why this recipe works

• Using milk instead of cream keeps it light while still tasting rich and creamy.
• A pinch of nutmeg brings out the creamy notes in the sauce.
• Aged Gruyere cheese gives it a rich, full flavor without having to use a ton.
• Panko breadcrumbs form an ultra crispy topping that is a great contrast to the soft zucchini.
• Adapted from the one and only Ina Garten.

Essential Ingredients

• Zucchini - Green zucchini, also known as courgettes, are the most commonly used, but this recipe can be made with any summer squash variety such as yellow zucchini, yellow squash, pattypan squash, Zephyr squash, Cousa squash, or 8 ball zucchini.
• Gruyere Cheese - Gruyere cheese is classic in gratins and gives great flavor to the zucchini. Comté, Jarlsberg, Emmental or a high quality Swiss cheese would all make good substitutes if you can't get Gruyere.
• Nutmeg - Freshly grated nutmeg is best, otherwise make sure your ground nutmeg is fresh and hasn't been sitting in your pantry for years. The flavor degrades over time so it won't have the same impact. If you can't remember when you bought it, it's time to get a new one.
• Breadcrumbs - My recipe calls for Panko breadcrumbs becuase I always have them on hand and they're always light and crunchy, but the original recipe calls for fresh breadcrumbs, so if you have them, use those instead.

Helpful Equipment

• Mandoline - A mandoline slicer makes it faster, easier to cut the zucchini and onions into even, uniform slices, which in turn will cook more evenly. I like to use a cut-proof glove instead of the guard that comes with the slicer because it's safer and more effective.

Step by step instructions

1. Preheat the oven to 400 degrees. 
2. Butter a small, shallow baking dish, about 7" x 10", or a 9-inch cast iron skillet and set aside.
3. Melt 3 tablespoons of butter in a large sauté pan over medium heat. Add the onions and cook for about 6-8 minutes, stirring occasionally, until they are softened but not browned. 
4. Add the zucchini, toss around, then cover and cook for about 8 minutes until softened. 
5. Add the salt, pepper and nutmeg, then sprinkle the flour over top and mix. 
6. Add the milk, stir and continue cooking until the mixture has thickened, about 3-4 minutes.
7. Pour the zucchini mixture into the prepared baking dish. 
8. Combine the breadcrumbs with the Gruyere cheese and sprinkle over the zucchini, then dot the remaining tablespoon of butter evenly over the top. 
9. Bake for about 20 minutes or until the top is golden brown and bubbling.
10. Sprinkle chopped parsley or chives over the top to garnish, if desired. Allow to cool at least 10 minutes before serving.

Tips for success

• If using very large zucchini from the garden, they can sometimes have tough skin and large, hard seeds. In this case, it's best to peel and remove the seeds with a spoon before slicing.
• For a richer, more decadent zucchini gratin, swap out the milk for heavy cream and double the cheese.
• If baking in a convection oven, lower the heat to 375 degrees F or the top could brown too quickly.
• If the top of the gratin isn't browned enough by the time it's finished baking, pop it under the broiler for a minute or two. Watch it carefully so it doesn't burn.

Faq about Zucchini Gratin

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Zucchini Gratin

This recipe for zucchini gratin features summer squash and onions in a creamy sauce topped with crispy, buttery breadcrumbs. It tastes light and rich at the same time with a delicate, mouthwatering flavor.

Prep Time: 10 minutes minutes

Cook Time: 40 minutes minutes

Total Time: 50 minutes minutes

Servings: 6 servings

Calories: 238kcal

Author: Nicole Gaffney

Ingredients

• 4 tablespoons unsalted butter divided, plus more for buttering the baking dish
• ½ lb yellow onions about 2 medium cut in half and sliced
• 1 lb zucchini 2 medium or 1 extra large, sliced ¼ inch thick
• 1 teaspoon salt
• ½ teaspoon freshly ground black pepper
• ⅛ teaspoon freshly grated nutmeg
• 2 tablespoons flour
• ½ cup whole milk
• ¾ cup panko or fresh bread crumbs
• ¾ cup grated Gruyere cheese
• Minced fresh parsley or chives to garnish optional

Instructions

1. Preheat the oven to 400 degrees.
2. Butter a small, shallow baking dish, about 7" x 10", or a 9-inch cast iron skillet and set aside.
3. Melt 3 tablespoons of butter in a large sauté pan over medium heat. Add the onions and cook for about 6-8 minutes, stirring occasionally, until they are softened but not browned.
4. Add the zucchini, toss around, then cover and cook for about 8 minutes until softened.
5. Add the salt, pepper and nutmeg, then sprinkle the flour over top and mix.
6. Add the milk, stir and continue cooking until the mixture has thickened, about 3-4 minutes.
7. Pour the zucchini mixture into the prepared baking dish.
8. Combine the breadcrumbs with the Gruyere cheese and sprinkle over the zucchini, then dot the remaining tablespoon of butter evenly over the top.
9. Bake for about 20 minutes or until the top is golden brown and bubbling.
10. Sprinkle chopped parsley or chives over the top to garnish, if desired. Allow to cool at least 10 minutes before serving.

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Notes

• If using very large zucchini from the garden, they can sometimes have tough skin and large, hard seeds. In this case, it's best to peel and remove the seeds with a spoon before slicing.
• For a richer, more decadent zucchini gratin, swap out the milk for heavy cream and double the cheese. 
• If baking in a convection oven, lower the heat to 375 degrees F or the top could brown too quickly. 
• If the top of the gratin isn't browned enough by the time it's finished baking, pop it under the broiler for a minute or two. Watch it carefully so it doesn't burn. 

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Nutrition

Calories: 238kcal | Carbohydrates: 19g | Protein: 9g | Fat: 15g | Saturated Fat: 9g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 4g | Trans Fat: 0.3g | Cholesterol: 41mg | Sodium: 621mg | Potassium: 328mg | Fiber: 2g | Sugar: 5g | Vitamin A: 575IU | Vitamin C: 16mg | Calcium: 240mg | Iron: 1mg