Ingredients:

  • 2 medium zucchini, thinly sliced (approximately 1 lb / 450g)
  • 1 medium eggplant, thinly sliced (approximately 1 lb / 450g)
  • 3 ripe tomatoes, thinly sliced (approximately 1.5 lbs / 680g)
  • 1 red bell pepper, thinly sliced (approximately 8 oz / 225g)
  • 1 yellow bell pepper, thinly sliced (approximately 8 oz / 225g)
  • 1 medium yellow onion, thinly sliced (approximately 6 oz / 170g)
  • 2 cloves garlic, minced
  • 2 tablespoons olive oil
  • 2 tablespoons all-purpose flour (25g)
  • 2 cups whole milk (475ml)
  • 1/2 cup heavy cream (120ml)
  • 1/4 cup grated Parmesan cheese (25g), plus extra for topping
  • 1/4 cup grated Gruyère cheese (25g)
  • 1 teaspoon dried thyme
  • 1/2 teaspoon dried oregano
  • 1/4 teaspoon nutmeg, freshly grated
  • Salt and freshly ground black pepper to taste
  • 2 tablespoons breadcrumbs (optional, for topping)
  • Fresh basil leaves, for garnish (optional)

Instructions:

  1. Wash and slice all vegetables thinly and evenly. If salting the eggplant, do so now.
  2. Heat olive oil in a large skillet over medium heat. Sauté onion until softened, then add garlic and cook until fragrant.
  3. Whisk in flour and cook for 1 minute. Gradually whisk in milk and cream until smooth. Bring to a simmer, stirring constantly. Reduce heat and simmer until slightly thickened.
  4. Remove from heat and stir in Parmesan, Gruyère, thyme, oregano, nutmeg, salt, and pepper. Taste and adjust seasonings as needed.
  5. Spread a thin layer of sauce in the bottom of the baking dish. Arrange vegetable slices in overlapping layers, alternating between zucchini, eggplant, tomatoes, peppers, and onion. Pour sauce evenly over the vegetables, making sure it seeps down between the layers.
  6. Sprinkle with additional Parmesan cheese and breadcrumbs (if using). Bake in a preheated oven at 375°F (190°C) for 45-50 minutes, or until the vegetables are tender and the top is golden brown and bubbly.
  7. Let the gratin rest for 10-15 minutes before serving. Garnish with fresh basil, if desired.