Step 1

Preheat oven to 375°F (190°C).

Step 2

Bring a large pot of salted water to boil. Add pasta and cook for 2 minutes shy of the package’s recommended cooking time; drain and set aside.

Step 3

Return pot to stove over medium-low heat and add oil. Add onion and caramelize until sweet and golden brown, about 30 minutes. Add garlic and sauté for an additional 2 minutes.

Step 4

Add chicken stock and squash; cover with lid and increase heat to medium-high. Cook for 5 minutes or until squash begins to soften. Add cauliflower; cover again and cook for 4 to 5 minutes or until vegetables fall apart easily when pricked with fork.

Step 5

Stir in milk and nutmeg. Transfer to a heatproof stand blender or use an immersion blender in pot to purée mixture until very smooth. (If using a stand blender, transfer mixture back to pot.)

Step 6

Heat pot over medium, stirring in 1 cup (250 mL) of the shredded cheddar and the Parmesan cheese. Stir gently until cheese is fully melted. Season with salt and pepper to taste.

Step 7

Add cooked pasta to sauce and stir until noodles are well coated.

Step 8

Transfer half of the mixture to an 8-inch (20 cm) square baking dish. Top with remaining shredded cheddar cheese. Add remaining noodles with cheese sauce; set aside.

Step 9

Add oil to a small non-stick skillet over medium heat. Add garlic and sauté until fragrant and golden, about 1 minute. Add bread crumbs and toss until fully coated.

Step 10

Remove bread crumbs from stovetop and mix with flaxseed, sage and Parmesan cheese. Spread evenly over casserole and bake for 25 to 30 minutes or until cheese sauce bubbles around edges and bread crumbs turn light brown. Sprinkle with fleur de sel.