Mediterranean Garden Zucchini Casserole

 

Vegan • Creamy • Garlic & Herb • Makes a generous long-pan casserole

Vegetables

• 1 large zucchini, peeled if the skin is tough, halved lengthwise and sliced about ¼-inch thick
  (If it is extremely large and seedy, scoop out the soft seed center first.)
• 2 medium sweet potatoes, peeled and cut into small cubes
• 2 carrots, thinly sliced
• 1 fresh red bell pepper, sliced or chopped
• 4–6 fresh chard leaves, stems removed and leaves chopped
• ½ small onion, thinly sliced
• 2–3 cloves fresh garlic, minced
• 6–8 mini tomatoes, halved, for dotting over the top
• 1–2 tablespoons extra-virgin olive oil

Mediterranean herb mixture

• 1 teaspoon garlic powder
• 1 teaspoon onion powder
• 1 teaspoon dried oregano
• ½ teaspoon dried marjoram
• ¼ teaspoon dried sage
• 1 tablespoon fresh rosemary, finely chopped
• 2 tablespoons fresh basil, chopped
• ¾ teaspoon salt, or to taste
• ½ teaspoon freshly ground black pepper

Rich Cashew Sauce

• 1½ cups raw cashews, soaked in hot water for 20–30 minutes and drained
• 1½ cups water or unsweetened plant milk
• 2 cloves fresh garlic
• 1 tablespoon extra-virgin olive oil
• 1 tablespoon lemon juice
• 1 tablespoon nutritional yeast
• ¾ teaspoon salt
• ¼ teaspoon black pepper
• ½ teaspoon garlic powder
• ½ teaspoon onion powder

For an especially rich sauce: use 1¼ cups liquid rather than 1½ cups. You want it pourable but quite thick, almost like a creamy Alfredo sauce.

Alternative #1: Make Walnut Sauce: Swap in raw, shelled walnuts for the cashews. Soak as you with the cashews (30 minutes) and use the same ingredients and directions to make the walnut sauce. Cashews and walnuts may both improve heart health by lowering blood pressure and triglycerides. Walnuts benefit brain health with high levels of omega-3 fatty acids. Cashews are higher in protein and lower in fats so could be seen as a better nut as per weight management.

You have an allergy to nuts? Thanks to a reader who asked, here is a simple, nut-free Hollandaise Sauce you can make instead (vegan-- no dairy or eggs)":

Alternative #2: Simple Nut-Free Vegan Hollandaise-Style Sauce

Ingredients for Hollandaise-Style Sauce:

• 1 cup unsweetened plain plant milk (soy or oat work well)
• 2 tablespoons cornstarch
• 1 tablespoon nutritional yeast
• 1 tablespoon vegan butter or extra-virgin olive oil
• 1 tablespoon fresh lemon juice
• 1/2 teaspoon garlic powder
• 1/4 teaspoon onion powder
• 1/2 teaspoon salt, or to taste
• 1/4 teaspoon turmeric, optional, for a lovely Hollandaise-yellow color
• A little black pepper

Directions for Hallandaise-Style Sauce:

1. In a small saucepan, whisk the plant milk and cornstarch together until completely smooth.
2. Whisk in the nutritional yeast, garlic powder, onion powder, salt, and optional turmeric.
3. Place over medium-low heat, stirring constantly.
4. Within a few minutes, the mixture will thicken into a smooth, creamy sauce.
5. Remove from the heat and whisk in the vegan butter or olive oil.
6. Stir in the lemon juice last. Taste and add a little more lemon or salt if desired.

For your casserole

I would use the sauce in exactly the same place as the cashew sauce:

Pour the warm Hollandaise-style sauce evenly over the assembled vegetables before baking.

Because this sauce is thickened with cornstarch rather than nuts, it should hold together nicely while baking. I would use about 1 1/4 cups plant milk if you want a particularly rich, spoonable sauce, or the full 1 1/2 cups for a somewhat more pourable coating.

One small change I'd make to your recipe: since the Hollandaise has a lovely lemony flavor, I'd leave the optional lemon juice at the end of the casserole, rather than adding it automatically. The sauce itself should provide enough brightness.

If you do opt for the Hollandaise-style sauce, you won't need to add any other lemon juice at the end of the baking-- the lemon in this saucy alternative contains lemon and is "bright enough"! 🌿🍋

Last Note re Nut Substitutes here:: You can also substitue cooked white beans that you have whirled up in the blender. Follow the rest of the recipe as is.

Mediterranean Garden Casserole Directions

1. Prepare the vegetables

Preheat oven to 400°F (200°C).

Place the sweet potato cubes and sliced carrots in a large bowl. Toss with about 1 tablespoon olive oil, a little salt and pepper, and a sprinkle of the dried herbs.

Spread on a baking sheet and roast for about 15 minutes.

Meanwhile, slice your giant zucchini.

A tip for a huge zucchini: If the flesh around the seeds is very soft or spongy, remove that center. You can save the firmer zucchini flesh for another recipe.

2. Make the cashew sauce

Put the soaked cashews, water or plant milk, garlic, olive oil, lemon juice, nutritional yeast, salt, pepper, garlic powder and onion powder into a high-speed blender.

Blend until very smooth and creamy.

Taste and adjust the salt, pepper or lemon juice. Set aside.

3. Sauté the flavor base

Heat a large skillet over medium heat.

Add a little olive oil, then add:

• sliced onion
• minced fresh garlic
• red bell pepper
• chopped chard

Cook for about 4–5 minutes, just until the vegetables begin to soften.

Add the fresh rosemary, basil, oregano, marjoram and sage. Stir for another minute.

4. Assemble

Lightly oil a long 9 × 13-inch baking dish (or a similar large casserole dish).

Arrange about half of the zucchini slices across the bottom.

Sprinkle with some of the herb mixture, salt and pepper.

Add the roasted sweet potatoes and carrots, followed by the sautéed pepper, onion and chard mixture.

Cover with the remaining zucchini.

Pour the rich cashew sauce evenly over everything. Use the back of a spoon to spread it into the vegetables.

Finally, scatter the halved mini tomatoes over the top like little red jewels. 🍅

Drizzle very lightly with olive oil and sprinkle with a little more black pepper and fresh basil.

5. Bake

Cover loosely with foil and bake at 375°F (190°C) for 30 minutes.

Remove the foil and bake another 20–25 minutes, until the zucchini is tender and the cashew sauce is bubbling and beginning to turn golden.

Let it stand for 10–15 minutes before serving. This gives the sauce time to thicken.

🌿 A little Veggie School secret

Because you're working with a large zucchini, I would resist putting it in completely raw and in very thick slices. Large zucchini can release a surprising amount of water. The brief roasting of the sweet potatoes and carrots also means that everything finishes cooking at approximately the same time.

And I think the combination of rosemary + basil + oregano + marjoram + just a touch of sage will give this a wonderfully old-fashioned Mediterranean garden flavor without any one herb overpowering the others.

Optional finishing touch: When it comes out of the oven, sprinkle the casserole with a little more fresh chopped basil and a few drops of fresh lemon juice. That should really brighten the rich cashew sauce. 🌱

If you like this casserole (and what is NOT to like? lol), perhaps you would like an additional 7 other vegan, plant-based casseroles that you can take to potlucks or serve at home.  Easy-to follow ebook format. No ads.

Check out the 7 Heavenly Casseroles HERE.

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🥤 Recipe and photos © 2026 Cynthia Zirkwitz | Veggie School
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