Turn turkey day extras into this easy, cheesy casserole from Food Network star Kelsey Nixon.
Preheat the oven to 350˚F. Butter a 9-by-13-inch baking dish.
Spread the bread out on a baking sheet. Toast in the oven until golden brown, stirring once halfway through, about 10 minutes. Remove from oven and let cool.
In a large pan over medium heat, melt butter, then add onion or leeks and cook until they soften and begin to caramelize, 8 to 10 minutes. Add mushrooms and ½ teaspoon salt and cook until soft, 5 minutes. Remove from heat and let cool.
In a large bowl, whisk together milk, cream, eggs, remaining ½ teaspoon salt, and pepper.
Toss toasted bread cubes, leek and mushroom mixture, Gruyere, turkey, cranberry, and thyme in the prepared baking dish. Pour milk mixture evenly over top, then press down with a rubber spatula, making sure the bread mixture is submerged in the custard. Let stand for at least 10 minutes, allowing the bread to soak up the custard. Top with Parmesan cheese just before baking.
Cover dish with foil and bake 20 minutes. Uncover and bake until center puffs up and sets, 20 to 25 more minutes. Let cool 5 minutes before serving.