1. Adjust 2 oven racks to the upper middle and lower middle positions and heat the oven to 325 degrees. Spread the bread out over 2 baking sheets and bake until dry and light golden brown, about 25 minutes, switching and rotating the baking sheets halfway through the baking time. Let the bread cool completely and then spread buter evenly over 1 side of each bread slice.
2. Meanwhile, cook the sausage in a medium nonstick skillet over medium heat, breaking the meat into small pieces with a wooden spoon, until beginning to brown, about 7 minutes. Stir in the shallots and cook until softened, about 3 minutes. Stir in the mushrooms and cook until their liquid is released, about 10 minutes. Transfer to a medium bowl and season with salt and pepper to taste. Add the wine to the skillet and simmer over medium-high heat until reduced to 1/4 cup, about 5 minutes; set aside to cool.
3. Butter a 13 by 9-inch baking dish and tightly fit half of the bread slices, buttered sides up, into a single layer in the dish. Sprinkle half of the sausage mixture, then 1 cup of the cheese evenly over bread slices. Repeat with the remaining bread slices, sausage mixture, and 1more cup of the cheese.
4. Whisk the eggs in a large bowl until combined, then whisk in the reduced wine, half-and-half, parsley, 1 teaspoon salt, and 1/2 teaspoon pepper. Pour the egg mixture evenly over the bread layers and sprinkle the remaining 1 cup cheese evenly over the top.
5. To Store: Wrap the strata tightly with plastic wrap, pressing the wrap flush to the surface of the strata. Weigh the strata down and refrigerate for at least 8 hours or up to 24 hours.
6. To Serve: Adjust an oven rack to the middle position and heat oven to 325 degrees. Meanwhile, unwrap the strata and let it sit at room temperature for 20 minutes. Bake the strata, uncovered, until puffed and the edges have pulled away slightly from the sides of the dish, about 1 hour and 20 minutes.