"Upgrade your average Thanksgiving leftovers by introducing this crowd-pleasing pasta bake, full of Gruye?re, mushrooms, and spinach, to the mix...."
olive oil, divided, plus more for dish
mezze rigatoni
large onion, chopped
cremini mushrooms, quartered
large cloves garlic, finely chopped
fresh thyme
spinach
fresh flat-leaf parsley, chopped
all-purpose flour
whole milk
Gruyère cheese, coarsely grated
cayenne
Kosher salt and pepper
shredded leftover cooked turkey or chicken