Description
How to make creamy zucchini tomato gratin with fresh herbs and melted cheese that turns summer vegetables into the most comforting layered dish.
Ingredients
Scale
Vegetables
- 3 medium zucchini, sliced into 1/4-inch rounds
- 4 large ripe tomatoes, sliced into 1/4-inch rounds
- 1 medium yellow onion, thinly sliced
- 3 cloves garlic, minced
Cheese Sauce
- 3 tablespoons butter
- 3 tablespoons all-purpose flour
- 1 1/2 cups whole milk, warmed
- 1 cup Gruyère cheese, grated
- 1/2 cup Parmesan cheese, grated
- 1/4 teaspoon nutmeg
Seasonings & Herbs
- 2 teaspoons kosher salt
- 1/2 teaspoon black pepper
- 2 tablespoons fresh thyme leaves
- 1/4 cup fresh basil, chopped
- 2 tablespoons olive oil
- 1/2 cup panko breadcrumbs
Instructions
- Prep Vegetables: Slice zucchini and tomatoes into 1/4-inch rounds. Toss zucchini with 1 teaspoon salt, let drain in colander for 15 minutes, then pat completely dry with paper towels.
- Make Sauce: Melt butter in saucepan over medium heat. Whisk in flour, cook 2 minutes. Gradually add warm milk, whisking constantly until smooth and thickened, about 5 minutes.
- Add Cheese: Remove sauce from heat. Stir in Gruyère, half the Parmesan, nutmeg, remaining salt, and pepper until cheese melts completely and sauce is silky smooth.
- Sauté Aromatics: Heat olive oil in large skillet over medium heat. Cook onion until softened and lightly golden, about 8 minutes. Add garlic, cook 1 minute until fragrant.
- Layer Gratin: Spread thin layer of cheese sauce in buttered 9×13 baking dish. Layer half the zucchini, onion mixture, tomatoes, thyme, and basil. Repeat layers, top with remaining sauce.
- Add Topping: Combine panko with remaining Parmesan, sprinkle over top. Cover with foil, bake at 375°F for 30 minutes. Remove foil, bake 15 minutes until golden and bubbly.
- Rest & Serve: Let gratin rest 10 minutes before serving to allow layers to set properly. The top should be golden brown and the sauce should be bubbling around the edges.
Notes
- Salt and drain zucchini for at least 15 minutes to prevent watery gratin.
- Warm milk before adding to roux to prevent lumps in cheese sauce.
- Assemble up to 24 hours ahead for easy entertaining – just add extra baking time.
- Let rest 10 minutes after baking for clean slices that hold their shape.
- Grate cheese fresh from block for better melting than pre-shredded varieties.
- Cover with foil first 30 minutes to prevent over-browning of top layer.
Allergy Information: Dairy, Gluten
Nutrition
- Calories: 285 calories
- Fat: 18g
- Carbohydrates: 16g
- Protein: 14g