Christmas/ Dinner/ Side dish/ Thanksgiving/ vegetarian dinner

Zucchini gratin (cheesy scalloped zucchini)

4 September 2020 | Last Updated: 14 September 2020

This zucchini gratin is an amazing side dish and a great way to use up lots of zucchini or summer squash. The zucchini is first browned in a pan then baked with a flavorful sauce and topped with bold-tasting cheese and crunchy breadcrumb and parmesan topping. I can not imagine zucchini ever tasting better!

close up picture of zucchini gratin in a baking dish
one serving of zucchini gratin on a blue plate with a fork on the side

Ingredients:

  • Zucchini – I used a zucchini and summer squash mix just because green and yellow colors look prettier together. Feel free to use just zucchini or just summer squash for this recipe.
  • Cheese – this is a really important ingredient of this dish. It takes it from ‘it’s good’ to ‘wow, this is amazing, what’s in it?!’. So I really encourage it to use bold-tasting cheese, like Gruyere cheese (this is what I used). Gruyere cheese is one of the best Swiss cheeses – it’s made from cow’s milk, it has a nutty, sharp taste and melts very well. Gruyere cheese can be unfortunately a little pricey so you could try to substitute it for American Swiss cheese/Emmental cheese. It’s important to choose cheese that melts easily. This website lists Jarlsberg cheese, Emmentaler cheese, Raclette cheese (this cheese probably melts too well for this recipe), Appenzeller cheese, Comte and Beaufort cheese as 5 best substitutes for Gruyere cheese.
  • If you don’t have Parmesan cheese on hand you can add more breadcrumbs, but the Parmesan adds lots of flavor to the dish. This crunchy breadcrumb-Parmesan topping is really amazing, it’s the same topping that I use to make this delicious chicken broccoli rice casserole.
ingredients needed to prepare zucchini gratin

Change it up:

  • Make it more calorie-friendly: I must admit this recipe is not very calorie-friendly. There’s lots of cream, cheese, butter, more cheese, and breadcrumbs 😉 If you would like, you can reduce the amount of the sauce a little, add half the shredded cheese, and half the crispy topping. I can assure you though, that if you’ll make the recipe as written you’ll be thrilled! This thing is really amazing.
  • Use other vegetables: broccoli or green beans would also work with this recipe. I would par-boil them first.
  • Other ingredients you could add: add sauteed onion to the sauce or top the casserole with crispy bacon crumbles.

How to make it step by step:

zucchini cut into slices on a chopiing board, sauteed zucchini in a pan

STEP 1: Cut the zucchini into thick slices – about 1/4-inch (7mm).

STEP 2: Brown the zucchini in a pan. This step is necessary – cooking the zucchini in oil adds so much flavor to this otherwise bland vegetable and also removes the excess water from it. Zucchini has really lots of water, so without removing it, the casserole would be too runny. Frying the zucchini doesn’t take up much time – I usually cook it simultaneously on two pans over high heat. The zucchini doesn’t have to be tender, just browned on both sides. The cooking time will depend on the pan type – non-stick pans take long to brown vegetables, also heavy-bottomed frying pans. The best would be here cast iron skillet or another frying pan with a thin bottom that browns the vegetables quickly. Another important thing is, don’t crowd the zucchini in the pan – you will be stewing it instead of frying, and getting these brown marks will take much longer. It’s also possible that such zucchini will be cooked through and too soft.

Alternatively you could roast the zucchini – toss it with olive oil and roast in an oven preheated to 445°F/230°C for about 10 minutes or put it under the broiler for a while. The other, more calorie-friendly method would be salting the zucchini, setting aside for about 30 minutes and patting dry with paper towels. Zucchini treated this way will lack some flavor, though.

sauteed zucchini in a baking dish, garlic with butter in a pan

STEP 3: Pat the zucchini with paper towels to remove excess fat then put in a large casserole dish.

STEP 4: Next, make the sauce. Remove the oil from the pan and add the butter. Cook finely chopped garlic in butter, then add the flour.

cream is being added to garlic in the pan, creamy white sauce in a pan

STEP 5: Add all the other ingredients for the sauce (milk, cream, mustard, lemon juice), and season with salt and pepper.

STEP 6: Cook the sauce just very briefly.

STEP 7: Make the breadcrumb topping: melt the butter, then stir in the breadcrumbs, then the Parmesan cheese.

a collage of three photos showing assembling steps of zucchini gratin

STEP 8 (photos 7, 8, 9): Assemble the casserole: Toss the zucchini with the sauce, top with shredded Gruyere cheese, then with the breadcrumb and Parmesan topping.

STEP 9: Bake at 375°F / 190°C for about 30 minutes until golden brown and bubbly. Set aside for about 10 minutes allowing the casserole to set a little, then dig in!

Enjoy!

overhead picture of zucchini gratin in an oval glass baking dish on a chopping board

Storing instructions:

This zucchini gratin can be easily stored and reheated. It will still taste amazing. Store it in the fridge for up to 4 days (cover the baking dish). Reheat the whole casserole or just a couple of servings in an oven. I’m putting the casserole in a cold oven and set it to 375°F/190°C, then bake for about 15 minutes. I like to turn on the fan at the end of the baking to dry out the topping and make it more crunchy, just as freshly made. If you don’t have this option in your oven, you can put it under the broiler for a couple of minutes (keep an eye on it so it won’t burn). If your oven warms up more quickly than mine to may need to reduce the temperature a little.

I don’t recommend freezing this casserole. Theoretically, it would work but the zucchini would be very mushy and soft instead of a little crunchy. So it could be fine for a casual dinner but not for an important occasion.

one serving of zucchini gratin on a light blue plate, fork on the side

What to serve it with:

This would be a perfect side dish to pair with roasted chicken, roasted turkey, or any of these recipes:

You could also serve this very simply. When I’m making it on Sunday and have leftovers, I serve them for a quick weeknight dinner just with mashed potatoes and sunny side up eggs. It’s such a delicious dinner.

Cheesy zucchini gratin

This zucchini gratin is an amazing side dish and a great way to use up lots of zucchini or summer squash.
zapiekanka z cukinii
Print Recipe
0 from 0 votes
Prep Time 30 minutes
Cook Time 30 minutes
Total Time 1 hour
Servings 6 servings
Calories 336kcal
Author Aleksandra

Ingredients

for the casserole:

  • 3.5 lbs (1.6kg) zucchini / summer squash 3 large zucchini or 6 small/medium zucchini
  • 4 tablespoons frying oil
  • 1 cup (100g) shredded cheese Gruyere/Swiss cheese, or other melting cheese of your choice

for the sauce:

  • 1 tablespoon butter
  • 5 cloves garlic finely chopped (not pressed)
  • 1.5 tablespoons flour
  • 1/2 cup milk 120 ml
  • 1/2 cup heavy cream 120 ml
  • 1 tablespoon lemon juice
  • 1 teaspoon Dijon mustard
  • salt and pepper to taste

breadcrumb topping:

  • 3 tablespoons butter 45g
  • 1/2 cup grated Parmesan cheese 45g
  • 1/2 cup breadcrumbs 55g

Instructions

  • Prepare the zucchini: Cut 3.5 lbs (1.6 kg) zucchini into 1/4-inch (7mm) slices. Next, brown the zucchini in a pan. Heat the oil in a big frying pan over high heat. When hot, add the zucchini slices in one layer and cook briefly only until browned, flip over using two forks, and brown the slices on the other side. The zucchini doesn't have to be tender and cooked through, just browned. Transfer the zucchini into a plate lined with paper towels and repeat with the remaining zucchini slices. I usually cook the zucchini simultaneously in two frying pans. Pat the zucchini with paper towels to remove the excess fat. Place the zucchini in a large oval baking dish (9×13-inch / 23x33cm).
  • Preheat the oven to 375°F / 190°C / Gas Mark 5 (no fan, if you have a convection oven reduce the temperature by about 20° or follow the manufacturer's instructions).
  • Make the sauce: wipe excess oil from the pan and add 2 Tbsp of butter. When it's bubbling add 5 finely chopped garlic cloves and cook for about 30 seconds over medium heat, until fragrant. Add 1.5 Tbsp of flour and cook, stirring, for about a minute. Add all the other ingredients for the sauce – 1/2 cup cream, 1/2 cup milk, 1 ts of mustard, and 1 Tbsp of lemon juice. Cook for about a minute. Season the sauce to taste with salt and pepper.
  • Make the breadcrumb topping: Melt 3 Tbsp of butter in a small pot, take the pot off the heat. Stir in 1/2 cup of breadcrumbs until combined, then 1/2 cup of grated Parmesan.
  • Assemble the dish: Add the sauce to the zucchini and stir together. Top with 1 cup shredded cheese, then with the breadcrumb topping.
  • Bake for about 30 minutes or until the breadcrumb topping is golden.
  • Let the casserole rest for about 10 minutes before cutting into servings.
  • Enjoy!

Notes

  • Instead of Gryuere cheese you can use Emmentaler cheese (Swiss cheese), Jarlsberg, Appenzeller cheese, Comte and Beaufort.
  • If you don’t have Parmesan cheese on hand you can add more breadcrumbs, but the Parmesan adds lots of flavor to the dish.
  • Use other vegetables: broccoli or green beans would also work with this recipe. I would par-boil them first.
  • Alternatively, you could roast the zucchini – toss it with olive oil and roast in an oven preheated to 445°F/230°C for about 10 minutes or put it under the broiler for a while. The other, more calorie-friendly method would be salting the zucchini, setting aside for about 30 minutes, and patting dry with paper towels. Zucchini treated this way will lack some flavor, though.
  • Storing instructions:
    This zucchini gratin can be easily stored and reheated. It will still taste amazing. Store it in the fridge for up to 4 days (cover the baking dish). Reheat the whole casserole or just a couple of servings in an oven. I’m putting the casserole in a cold oven and set it to 375°F/190°C, then bake for about 15 minutes. I like to turn on the fan at the end of the baking to dry out the topping and make it more crunchy, just as freshly made. If you don’t have this option in your oven, you can put it under the broiler for a couple of minutes (keep an eye on it so it won’t burn). If your oven warms up more quickly than mine to may need to reduce the temperature a little. I don’t recommend freezing this casserole. Theoretically, it would work but the zucchini would be very mushy and soft instead of a little crunchy. So it could be fine for a casual dinner but not for an important occasion.
  • Calories = 1 serving (1/6 of the recipe). This is only an estimate!
Course Side Dish
Cuisine American, international
Keyword cheesy zucchini gratin, scalloped zucchini, zucchini casserole, zucchini gratin

Did you make this recipe? Let me know how you liked it and give it a star rating in the comments below! You can also add a photo of your creation!

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