Instructions

1. Heat the oil in a heavy large skillet over medium heat. Add the sausage and cook about 5 minutes, breaking it up into small pieces with a wooden spoon. Add the shallots and sauté until translucent, about 3 minutes. Add the apple and the spinach and sauté over medium-low heat for another 2 minutes. Set aside to cool slightly.
2. Place half of the bread cubes in a buttered 3-quart baking dish. Sprinkle half of the mozzarella over the bread, then top with half of the spinach mixture. Repeat layering.
3. Whisk the milk, cream, eggs, salt, and pepper in a large bowl and pour evenly over the strata. Top with the Parmesan cheese. Chill the strata, covered with plastic wrap, at least 2 hours and up to 12 hours.
4. Preheat the oven to 350°F. Bake the strata uncovered until puffed, golden brown, and cooked through, about 50 minutes. A thin knife inserted in the middle of the strata should come out clean. If the top browns too quickly, cover with a sheet of aluminum foil. Let stand 5 minutes before serving.