Ingredients
Equipment
Method
- Preheat your oven to 400°F (200°C). Lightly grease a 9x13 inch baking dish.
- Bring a large pot of salted water to a boil. Add the chopped root vegetables and blanch for 5-7 minutes until they are slightly tender but still have a firm bite. Drain them thoroughly and set aside.
- In a large saucepan or Dutch oven, melt 4 tablespoons of butter over medium heat. Add the chopped onion and cook, stirring occasionally, until soft and translucent, about 5-6 minutes. Add the minced garlic and fresh thyme leaves and cook for another minute until fragrant.
- Sprinkle the flour over the cooked onions. Whisk constantly for 1-2 minutes to cook out the raw flour taste, forming a roux.
- Slowly, while whisking continuously, pour in the vegetable broth until smooth. Gradually whisk in the whole milk and then the heavy cream. Bring the mixture to a gentle simmer, and let it cook for a few minutes until it has thickened enough to coat the back of a spoon.
- Remove the saucepan from the heat. Stir in the grated Gruyère and half of the Parmesan cheese (1/4 cup) until they are completely melted and the sauce is smooth. Season with 1 teaspoon salt, 1/2 teaspoon black pepper, and the nutmeg. Taste the sauce and adjust seasonings as needed.
- Gently fold the par-cooked vegetables into the cheese sauce, ensuring every piece is generously coated. Pour the mixture into your prepared baking dish and spread it into an even layer.
- In a small bowl, melt the remaining 1 tablespoon of butter. Add the panko breadcrumbs and the remaining Parmesan cheese (1/4 cup) and toss to combine. Sprinkle this mixture evenly over the top of the casserole.
- Bake for 25-30 minutes, or until the sauce is bubbly and the topping is golden brown and crisp. Let the casserole rest for 10-15 minutes before serving to allow the sauce to set up.
Notes
Expert Tips:
- Cut vegetables into a uniform 1-inch size for even cooking.
- Grate your own cheese from a block for the smoothest, creamiest sauce.
- Don't skip blanching the vegetables; it ensures they are perfectly tender in the final dish. Variations & Substitutions:
- Protein Boost: Add a can of rinsed chickpeas or white beans, or stir in shredded rotisserie chicken for a non-vegetarian option.
- Add Greens: Stir in a few handfuls of fresh spinach or kale into the sauce before pouring it over the vegetables.
- Spice it Up: Add a pinch of cayenne pepper or a teaspoon of smoked paprika to the sauce for a smoky heat.
- Ingredient Swaps: Feel free to use other root vegetables like celery root or Yukon Gold potatoes. Sharp white cheddar or fontina can replace Gruyère. Rosemary or sage can be used instead of thyme.
- Cut vegetables into a uniform 1-inch size for even cooking.
- Grate your own cheese from a block for the smoothest, creamiest sauce.
- Don't skip blanching the vegetables; it ensures they are perfectly tender in the final dish. Variations & Substitutions:
- Protein Boost: Add a can of rinsed chickpeas or white beans, or stir in shredded rotisserie chicken for a non-vegetarian option.
- Add Greens: Stir in a few handfuls of fresh spinach or kale into the sauce before pouring it over the vegetables.
- Spice it Up: Add a pinch of cayenne pepper or a teaspoon of smoked paprika to the sauce for a smoky heat.
- Ingredient Swaps: Feel free to use other root vegetables like celery root or Yukon Gold potatoes. Sharp white cheddar or fontina can replace Gruyère. Rosemary or sage can be used instead of thyme.