• Grease a 13-by-9-inch baking dish with unsalted butter. Set it aside.
• Preheat the oven to 400°F. Add the cubed butternut squash to a baking sheet. Drizzle the butternut squash with olive oil, and roast the squash until browned and tender, about 30 minutes.
• In a large nonstick pan set over medium heat, cook the sausage, using a spatula to break it apart into crumbles. Remove it to a paper towel-lined plate and drain any drippings from the pan.
• To the same pan the sausage was cooked in, add the butter. Over medium heat, melt the butter then add the diced onions and cook, stirring occasionally, until they are softened, 3 to 5 minutes.
• Transfer the cooked onions to a medium bowl then stir in the cooked sausage, roasted squash, fresh sage and cubed bread. Stir together the mixture then transfer it to the greased baking dish.
• In a large bowl, whisk together the eggs, milk, salt and pepper.
• Pour the egg mixture over the layers of bread and sausage. Cover the dish securely with plastic wrap and refrigerate it overnight, or for about 8 hours. (See Kelly's Note.)
• Remove the strata from the fridge, discard the plastic wrap, and let it rest at room temperature for 30 minutes.
• Preheat the oven to 350ºF. Place the strata on a baking sheet and bake it, uncovered, for 35 to 45 minutes, or until the eggs are fully cooked. Let the strata rest for 5 minutes before slicing and serving.

Kelly's Note:

• In a rush? No need to let the casserole sit overnight! Simply prepare it according to the recipe directions then bake it immediately until the eggs are cooked through.
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