Ingredients:
- 1 tablespoon (15 ml) olive oil
- 1 medium yellow onion, chopped (approx. 1 cup or 150g)
- 2 cloves garlic, minced (approx. 2 tsp or 6g)
- 1 medium carrot, peeled and diced (approx. ½ cup or 75g)
- 1 stalk celery, diced (approx. ½ cup or 75g)
- 1 red bell pepper, seeded and diced (approx. 1 cup or 150g)
- 1 zucchini, diced (approx. 1 cup or 150g)
- 1 yellow squash, diced (approx. 1 cup or 150g)
- 8 ounces (225g) cremini mushrooms, sliced
- 1 teaspoon (5 ml) dried thyme
- ½ teaspoon (2.5 ml) dried rosemary
- Salt and freshly ground black pepper to taste
- 4 tablespoons (57g) unsalted butter
- 4 tablespoons (32g) all-purpose flour
- 3 cups (710 ml) whole milk
- ½ teaspoon (2.5 ml) nutmeg, freshly grated
- ½ cup (50g) grated Parmesan cheese
- ½ cup (120 ml) heavy cream
- 2 tablespoons (28g) unsalted butter, melted
- 1 cup (100g) panko breadcrumbs
- ¼ cup (25g) grated Parmesan cheese
- 2 tablespoons (15g) chopped fresh parsley
Instructions:
- Heat olive oil in a large skillet. Sauté onion and garlic until softened. Add carrot and celery, cook until slightly tender.
- Add bell pepper, zucchini, yellow squash, and mushrooms. Cook until vegetables are tender-crisp and mushrooms have released their moisture. Season with thyme, rosemary, salt, and pepper. Set aside.
- Melt butter in a saucepan. Whisk in flour and cook for 1 minute to create a roux. Gradually whisk in milk until smooth. Bring to a simmer, stirring constantly, until thickened.
- Remove from heat and stir in nutmeg, Parmesan cheese, and heavy cream. Season with salt and pepper to taste.
- Combine the cooked vegetables with the cream sauce. Pour into the prepared baking dish.
- In a small bowl, combine melted butter, panko breadcrumbs, Parmesan cheese, and parsley. Mix well.
- Sprinkle the breadcrumb mixture evenly over the vegetable casserole.
- Bake in a preheated oven at 375°F (190°C) for 30-35 minutes, or until golden brown and bubbly. Let stand for 10 minutes before serving.