Preheat oven to 375 degrees F.

• 4 cups butternut squash, sliced into 3/4-inch squares
• 1 tbsp. olive oil
• 2 leeks, tops removed and washed, green and white part thinly sliced
• 2 to 3 cloves garlic
• 1/4 cup butter
• 1 pound crimini mushrooms, quartered into bite-size pieces
• 2 tbsp. fresh thyme leaves, chopped
• Salt and pepper to taste
• 6 cups cubed artisan bread, cut into 1-inch pieces
• 2 tbsp. flour
• 3 1/2 cups half and half
• 5 large eggs
• 1/3 cup Parmesan cheese, grated
• 1 1/2 cups Gruyére cheese, grated

Toss squash with olive oil until well coated. Place squash on sheet tray lined with parchment paper, and roast 30 to 35 minutes, until tender. Toss squash after 15 minutes so it cooks evenly. While squash is cooking, sauté leeks and garlic in 1 tablespoon butter until brown. Remove to a large bowl. 

Using the same pan, add 1 tablespoon butter and sauté mushrooms until brown; add thyme. Add mushrooms and roasted squash to leeks. Salt and pepper to taste.

Briefly toast bread cubes in oven and add to squash mixture.  Mix well. Place bread and squash mixture into a well-buttered casserole dish or a 13 x 9-inch pan. Set aside.

In a sauté pan melt remaining butter; add flour and cook over medium heat 2 to 3 minutes. Whisk in 1 1/2 cups half and half and bring to a boil. In a separate bowl, whisk remaining half and half with eggs and Parmesan cheese. Slowly add heated half and half; stir to combine. Pour over squash mixture and sprinkle top with Gruyére cheese.

Bake uncovered 30 minutes, until the cheese is melted and slightly browned. Serves 8.

NOTE: You can make this dish a day ahead, and instead of baking it, cover and place in the refrigerator overnight to let the flavors meld. Bring to room temperature before baking.