Butternut Squash Casserole

1 butternut squash
2 Tablespoon olive oil
2 tablespoons finely chopped thyme
Salt and pepper
1 tablespoon butter
2-3 leeks, white and light green parts only, halved lengthwise and thinly sliced crosswise
6 eggs
2 1/2 cups half-and-half
1/4 cup Parmesan, grated
8 oz. baguette, cut into 1/2 inch dice
4 oz. prosciutto, cut into very small pieces (optional)

Heat your oven to 400° and butter a 9x13 inch baking dish. Toss the butternut with 1 tablespoon of the olive oil and the thyme. Spread on a baking sheet and roast in the oven for about 25 minutes until cooked through. Set aside and let cool completely.  In the meantime, melt the butter and remaining 1 tablespoon olive oil in a skillet. Add the leeks and season with salt and pepper. Cook over moderate heat, stirring frequently for about 20 minutes until very soft and tender. In a large bowl, beat the eggs with the half and half, cheese, 1 teaspoon of salt and a 1/2 teaspoon pepper. Add the bread and let sit for 10 minutes, or until soaked through. Fold in the squash, leeks and prosciutto. Pour into your baking dish and bake for an hour, until lightly golden on top. Let sit for 15 minutes before serving.