Preheat the oven to 425 degrees F

Cut the squash into quarters, then carefully remove the skin using a heavy-duty knife. Cut the squash into 1-centimetre wedges, and cut the (washed) leeks into 1-centimetre slices.

On a large baking sheet, toss the squash and leeks with olive oil and 1/2 teaspoon of salt, and roast until the squash is soft but not mushy. About 20 minutes

Remove the baking sheet from the oven, reduce the oven temperature to 375 degrees, and allow the squash and leeks to cool while you make the egg mixture.

In a medium bowl, whisk together the eggs, milk, the remaining 1/2 teaspoon of salt, and pepper until you get a nice smooth mixture.

Spray a 9 x 13 baking dish with non-stick spray. If you're worried about your omelette sticking, you can also line the bottom of the pan with a sheet of parchment paper

Arrange the squash and leeks in the bottom of the baking dish, and pour the egg mixture over them. If using parmesan cheese, now. is the time to sprinkle it over the top of the omelette.

Bake the whole thing at 375 F for 20-30 minutes, or until the top is slightly golden and the middle is no longer runny.