Thanksgiving Pot Pie

Name: Thanksgiving Pot Pie
Ingredients: 5 tablespoons all-purpose flour, plus additional for dusting; 1 sheet frozen puff pastry, thawed; Nonstick cooking spray, for the baking dish; 5 tablespoons unsalted butter; 2 celery stalks, thinly sliced; 1 medium yellow onion, diced; 1 rotisserie turkey breast, shredded (about 4 cups); 4 cups low-sodium chicken or turkey broth; 1 cup half-and-half; 1 cup shredded Brussels sprouts; 1 cup stuffing mix; 1 teaspoon kosher salt; 1/2 teaspoon freshly ground black pepper; 1/2 cup whole cranberry sauce; 1 large egg, whisked