A gratin is a dish topped with a golden browned crust of breadcrumbs and/or melted cheese. In France, gratins are generally made with potatoes. This Easy Make Ahead Zucchini Gratin is an amazing deviation which will have you coming back for more!
When I got home from work, the proverbial question arose – “What’s for dinner?” Given that there are two tropical systems that could impact us within the week, I thought about making something that could be frozen for hurricane ready meals.
As it turned out, I had some zucchini that needed to be used – thus the Easy Make Ahead Zucchini Gratin was born! All through dinner, the Master Taste Tester kept commenting on how good it was – the ultimate compliment!
Estimated reading time: 6 minutes
Table of Contents
Ingredients for Easy Make Ahead Zucchini Gratin
I used the following ingredients: Grated Gruyère cheese, Panko breadcrumbs, zucchini, onion, Kosher salt, unsalted butter, freshly ground black pepper, freshly ground nutmeg, all-purpose flour and milk.
Making the Easy Make Ahead Zucchini Gratin
Step 1: I started by combining the Gruyère cheese and Panko breadcrumbs in a small bowl.
Step 2: Then, I grated the zucchini and onion in my food processor.
Step 3: I transferred the zucchini and onion to a wire mesh strainer set over a bowl and sprinkled on some salt.
The idea here was to remove as much of the liquid as possible from both the zucchini and the onion.
Step 4: After 30 minutes, I squeezed liquid from the zucchini and onion with my hands. Then, I placed the grated zucchini and onion in a paper towel and continued squeezing as much liquid as possible from them.
I was amazed that I ended up with about a cup of liquid! This is significant because the dish would have otherwise been incredibly watery had the liquid not been removed!
Step 5: I heated unsalted butter in a 12-inch skillet over medium-high heat until it was foaming. Then, I added the squeezed zucchini and onion and cooked it for about 5 minutes until it was just tender.
After that, I added the remaining salt, pepper, nutmeg and flour and stirred the mixture to combine everything.
Step 6: After about a minute, I added the milk and stirred the mixture until it was thickened and bubbly.
Step 7: I transferred the zucchini mixture to a casserole dish that I had sprayed with non-stick spray. Then, I topped it with the Gruyère/Panko mixture.
Finally, I dotted the zucchini gratin with some additional unsalted butter. At this point, I could have refrigerated the zucchini gratin for a later use.
Instead, I popped the zucchini gratin into a preheated 400° F oven for about 20 minutes. After 20 minutes, it was bubbling hot, golden brown and absolutely delicious. Yum!
Frequently Asked Questions
The zucchini and onion can be grated using the largest holes in a box grater if you don’t have a food processor.
I happened to have fresh nutmeg, so I used it. I could have also used ground nutmeg.
Zucchini is a summer squash that is actually a fruit. It’s grown throughout the US during the warm summer months. While you may think of zucchini as a vegetable it is actually a fruit. Zucchini is low in calories and a good source of vitamins A and C, fiber and potassium.
Courgette is another name for zucchini.
You can substitute Swiss cheese, Cheddar cheese, Monterey Jack and Fontina cheese for the Gruyère cheese.
Plain breadcrumbs can be easily substituted for the Panko breadcrumbs. The topping will not be quite as crispy though.
This Easy Make-Ahead Zucchini Gratin makes excellent leftovers. If you want the cheese/panko topping to be crisp, you should reheat it in a 350°F oven for about 15 minutes or until heated through.
You can make this amazing casserole several hours to a day before baking it. Cover it with aluminum foil and refrigerate. Add about 5 minutes to the baking time if baking it from the refrigerator.
Other Delicious Zucchini Recipes
If you’re a fan of zucchini, you should definitely check out these amazing recipes:
- Crispy Parmesan Zucchini Fries
- Easy Cheesy Zucchini Bites
- Three Cheese Zucchini Tart
- Creamy Puréed Zucchini Soup
I first posted this amazing recipe on September 6, 2017. Since then, it’s been one of my favorite vegetable casseroles.
This post includes the same delicious recipe with updated text and photos.
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Easy Make Ahead Zucchini Gratin
- ½ cup (2 ounces) grated Gruyère cheese (See Tip 1)
- ½ cup (1.5 ounces) Panko breadcrumbs (See Tip 2)
- 2 large zucchini, about 1 pound total
- 1 large onion (between 8 and 9 ounces)
- 1 teaspoon Kosher salt, divided
- 4 Tablespoons butter, divided
- 1 ½ Tablespoons all-purpose flour
- ¾ cup (6-ounces) milk
- ¼ teaspoon freshly ground black pepper
- ⅛ teaspoon freshly ground nutmeg (See Tip 3)
- Preheat oven to 400° F. Spray a casserole dish with nonstick spray. Set aside.
- Combine Gruyère and Panko breadcrumbs in a bowl; set aside.
- Scrub zucchini under cold water; cut off the two ends, but do not peel. Cut off two ends of onion, and peel. Grate the zucchini and onion in food processor of box grater; toss with ½ teaspoon salt in a colander. Let sit for 30 minutes.
- Squeeze liquid from zucchini and onion with hands. Then place in double paper towel and continue squeezing as much liquid as possible. (See Tip 4)
- Heat 3 tablespoons of the butter to foaming over medium heat in a 12-inch nonstick skillet. Add the grated zucchini and onion. Cook for 3 to 5 minutes, just until tender. Season with remaining ½ teaspoon of salt, pepper nutmeg. Add flour; stir well to combine and cook for a minute or two.
- Add milk; stir constantly until thickened and bubbly. Correct seasonings.
- Transfer zucchini mixture to prepared casserole dish. Top with Gruyère/Panko mixture. Dot with remaining tablespoon of butter. Can be made ahead of time up to this point. (See Tip 5)
- Bake in a preheated 400º F oven for 20 minutes or until bubbling hot and golden browned. Yield: 4 servings. (See Tip 6)
Chula’s Expert Tips
- May substitute Swiss cheese, Cheddar cheese, Monterey Jack cheese or Fontina cheese for the Gruyère cheese.
- May use plain breadcrumbs in place of the Panko.
- May use store-bought ground nutmeg in place of the freshly ground nutmeg.
- You’ll be surprised at the amount of liquid that you can squeeze from the zucchini and onion! The reserved liquid from the zucchini and onion can be used in sauces or gravies.
- If made ahead of time, cover and refrigerate for up to a day. Add 5 minutes to the baking time
- Leftovers, if any, can be reheated in a 350°F oven for 10 to 15 minutes. They can also be reheated in the microwave for several minutes. However, if reheated in the microwave, the cheese toping will lose its crispiness.