Creamy Cheesy Zucchini & Potato Gratin
Nobody wants a dry, bland casserole, and this Creamy Cheesy Zucchini & Potato Gratin avoids both with thin, tender potato and soft zucchini under a silky cheese sauce that soaks into every layer. The top bakes golden and bubbly, making it a strong side for roast chicken or pork chops.
Yield: 6 servings | Prep: 25 min | Bake: 40 min | Total: 65 min
Creamy Cheesy Zucchini & Potato Gratin Ingredients
- 2 tbsp unsalted butter — Butter starts the sauce and gives it a nutty, rich base. Melt it over medium heat before adding the garlic.
- 3 cloves garlic, minced — Garlic goes in early so it mellows into the butter instead of burning.
- 2 tbsp all-purpose flour — Flour cooks with the butter and garlic into a roux that thickens the sauce so it clings to the vegetables.
- 1 1/2 cups heavy cream (360 ml) — Heavy cream gives the sauce body and helps it stay smooth in the oven.
- 1/2 cup whole milk (120 ml) — Milk thins the sauce just enough to pour evenly between the layers.
- 1/2 tsp garlic powder — Reinforces the garlic flavor through the sauce without adding moisture.
- 1 tsp Italian seasoning — Adds herby warmth that pairs well with zucchini.
- 1/2 tsp dried thyme — A small amount adds an earthy note that rounds out the cheese.
- 1/2 tsp salt — Seasons the sauce and the layers. The cheeses are salty, so taste before adding more.
- 1 tsp pepper — Adds a gentle bite that keeps the richness in check.
- 1 cup shredded mozzarella (100 g), divided — Melts into a smooth, stretchy layer. Half goes into the sauce and half goes on top.
- 1 cup shredded Gruyère (100 g), divided — Adds a nutty, savory depth. Half goes into the sauce and half goes on top.
- 3 medium zucchini, thinly sliced — Zucchini adds a light, fresh bite that balances the rich sauce. Slice about 1/8 inch thick so it cooks at the same pace as the potatoes.
- 4 medium potatoes, thinly sliced — Potatoes form the body of the dish and soak up the cream as they bake. Slice them to the same thickness as the zucchini.
- 1/2 cup grated Parmesan (50 g) — Browns on top for a crisp, golden finish.
- 2 tbsp fresh parsley, chopped — Added at the end for a bright, fresh finish.
Substitutions And Additions
Gruyère
Sharp white cheddar or Swiss can stand in for Gruyère at the same amount. Cheddar gives a tangier flavor, and Swiss melts slightly less smoothly, so the sauce may look a bit grainier.
Heavy Cream
Half-and-half can replace heavy cream, but the sauce will be thinner and may need a few extra minutes of bubbling on the stove to thicken. Light cream is more likely to separate in the oven, so it is not recommended.
Zucchini
Yellow summer squash can replace zucchini in the same amount. It is slightly softer and sweeter, so the top may brown a little faster.
Potatoes
Yukon Gold potatoes hold their shape well and taste buttery. I’d avoid russets here, since they break down more and make the gratin softer.
How To Make This Creamy Cheesy Zucchini & Potato Gratin Recipe
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Build the roux. Melt the 2 tbsp unsalted butter in a saucepan over medium heat. Add the 3 minced garlic cloves and cook about 1 minute, stirring, until fragrant but not browned. Stir in the 2 tbsp all-purpose flour and cook 1 minute more, until it smells toasty and forms a thick paste.
Keep the heat at medium so the garlic does not scorch, which would make the sauce bitter.
Make the cream sauce. Slowly whisk in the 1 1/2 cups (360 ml) heavy cream and 1/2 cup (120 ml) whole milk. Add the liquid gradually at first so no lumps form in the flour. Keep whisking until the sauce bubbles around the edges and lightly thickens, about 3 to 5 minutes.
If lumps appear, whisk vigorously off the heat and then return the pan to medium heat.
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Season and melt the cheese. Whisk in the 1 tsp Italian seasoning, 1/2 tsp dried thyme, 1/2 tsp garlic powder, 1/2 tsp salt, 1 tsp pepper, and half of the mozzarella and Gruyère. Stir until the cheese has fully melted and the sauce is smooth and glossy. Keep the heat moderate; overheating causes the cheese to separate and turn grainy.
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Prepare the baking dish. Grease a baking dish. Set the thinly sliced potatoes and zucchini on the counter so they are ready to layer.
Layer the vegetables. Arrange the potatoes and zucchini in tight, overlapping rows, alternating them so the layers are even. Pour the cheese sauce evenly over the top, letting it seep down between the slices.
Slice everything to a consistent thickness so the potatoes and zucchini finish cooking together.
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Top the gratin. Sprinkle the remaining mozzarella, the remaining Gruyère, and the 1/2 cup (50 g) grated Parmesan over the top.
Bake. Bake at 400°F (200°C) for 40 minutes, until bubbly around the edges and golden-brown on top. Test a potato slice with a knife; it should slide in easily, which means the vegetables are tender. If the center is still firm, bake a few minutes longer.
Rest and garnish. Let the gratin rest about 10 minutes so the sauce sets for clean portions. Garnish with the 2 tbsp chopped fresh parsley and serve warm.
How To Serve And Store
Serve this gratin warm alongside roast chicken, pork chops, or a green salad with a sharp vinaigrette.
In The Fridge
Cool the gratin to room temperature, then cover and refrigerate for up to 4 days. Reheat individual portions in a 350°F (175°C) oven until hot throughout, or microwave in short bursts.
In The Freezer
This gratin does not freeze well, because the cream sauce can turn grainy and the potatoes soften when thawed. Enjoy it within 4 days of baking.
Frequently Asked Questions
Can you make this gratin ahead?
Yes. Assemble it and refrigerate it unbaked for up to 24 hours. Bring it to room temperature for about 20 minutes, then bake as directed, adding a few extra minutes if the center is still cold.
How do I know when the gratin is done?
It is done when the top is golden-brown, the sauce bubbles around the edges, and a knife slides easily through the potatoes.
Why did my sauce look grainy?
Graininess usually means the cheese was overheated and separated. Keep the heat moderate when melting the cheese and stir gently until smooth.
More Recipes You’ll Love
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- Cheesy Zucchini Mozzarella Bites
- Creamy Cheesy Potato Pie with Chicken & Mushrooms
Thanks for cooking along with Hailee Recipes. Follow Hailee Recipes on Pinterest for more easy side dishes.
Creamy Cheesy Zucchini & Potato Gratin
Ingredients
Method
- Melt the 2 tbsp unsalted butter in a saucepan over medium heat; add the 3 cloves minced garlic and cook about 1 minute until fragrant but not browned; stir in the 2 tbsp all-purpose flour and cook 1 minute more until toasty and paste-like; slowly whisk in the 1 1/2 cups (360 ml) heavy cream and 1/2 cup (120 ml) whole milk until smooth; keep whisking until bubbling around the edges and lightly thickened, about 3 to 5 minutes.
- Whisk in the 1 tsp Italian seasoning, 1/2 tsp dried thyme, 1/2 tsp garlic powder, 1/2 tsp salt, 1 tsp pepper, and half of the mozzarella and Gruyère; stir until fully melted, smooth, and glossy.
- Grease a baking dish; arrange the thinly sliced potatoes and zucchini in tight, overlapping rows; pour the cheese sauce evenly over the top, letting it seep between the slices.
- Sprinkle the remaining mozzarella, the remaining Gruyère, and 1/2 cup (50 g) grated Parmesan over the top; bake at 400°F (200°C) for 40 minutes until bubbly around the edges and golden-brown; rest about 10 minutes, then garnish with the 2 tbsp chopped fresh parsley.
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