Roasting the squash before layering it in the gratin enhances its flavour. This step also cuts down on Turkey Day prep—just sprinkle on the topping and pop it into the oven after the turkey comes out.

MAKES: 10 servings
PREP TIME: 20 minutes
TOTAL TIME: 1 hour and 30 minutes

INGREDIENTS

• 1 squash about 2kg, peeled, seeded and cut in 3/4-inch (2 cm) cubes
• 2 teaspoons olive oil
• 1 teaspoon salt
• 1/2 teaspoon pepper
• 2 tablespoons butter
• 1 cup sliced leek white and light green parts only
• 2 cloves garlic grated or pressed
• 1 1/2 teaspoon chopped fresh thyme
• 1/4 cup all-purpose flour
• 2 cups milk
• 2 teaspoons Dijon mustard
• pinch nutmeg
• 2 cups shredded old Cheddar cheese

METHOD

In large bowl, toss together squash, oil and 1/4 tsp each of the salt and pepper; arrange in single layer on lightly greased foil-lined rimmed baking sheet. Roast on bottom rack of 450°F (230°C) oven, tossing once, until tender and edges are light golden, 20 to 25 minutes. Transfer to greased 8-cup (2 L) baking dish.

While squash is roasting, in saucepan, melt butter over medium heat; cook leek, stirring often, until softened, about 3-4 minutes. Add garlic and 1 tsp of the thyme; cook for 1 more minute. Sprinkle with flour; cook, whisking constantly, for 1 minute. Whisk in milk, mustard, nutmeg and remaining salt and pepper; bring to boil. Reduce heat and simmer, stirring, until thick enough to coat back of spoon, about 1-2 minutes. Stir in 1 cup of the Cheddar.

Pour leek mixture over squash. (Make-ahead: Cover and refrigerate for up to24 hours. Let stand at room temperature for 1 hour before continuing with recipe.) Sprinkle with remaining Cheddar and thyme. Cover and bake in 425°F (220°C) oven for 30 minutes; uncover and bake until top is browned, 15-20 minutes.