Heat the oven to 375°F and butter a 9-by-13-inch baking dish with 1 teaspoon of the butter.
Boil the spaghetti for 2 minutes less than the package directs, then drain it.
Melt 2 tablespoons butter in a large skillet over medium-high heat and cook the mushrooms for 6 to 8 minutes, until browned and dry at the edges.
Add the remaining butter, whisk in the flour and cook for 1 minute.
Whisk in the broth, half-and-half and sherry gradually, then add the salt and pepper and simmer for 4 minutes, until the sauce coats a spoon.
Fold in the turkey, spaghetti and 1/2 cup Parmesan and spread the mixture in the dish.
Top with the remaining Parmesan and the almonds and bake for 25 to 30 minutes, until the center reaches 165°F and the almonds are golden.
Rest for 5 minutes before serving.
