Preheat your oven to 375°F (190°C) and grease your casserole dish.

In a large skillet, heat butter and olive oil over medium heat. Sauté onions for about 5 minutes until translucent.

Add diced bell peppers and minced garlic. Cook for an additional 4–5 minutes until softened.

Add sliced mushrooms and cook for 3–4 minutes. Stir in chopped tomatoes and fresh herbs, simmer for 2 minutes.

Add cubed eggplant, season with salt and olive oil. Sauté for 8–10 minutes until soft and browned.

Sprinkle in the flour and mix thoroughly to coat. Fold in the tomato mixture and simmer for 3 minutes.

Transfer the vegetable mixture into the greased casserole dish and spread it evenly.

Layer mozzarella or Parmesan cheese over the top, covering the veggies completely.

Bake uncovered for 30 minutes until the cheese is bubbly and golden.

Let the casserole rest for 5 minutes before serving.