kosher salt, plus more for the pasta
jumbo pasta shells (25 to 30)
olive oil
cremini mushrooms, thinly sliced
fresh thyme, chopped
garlic cloves, minced
16-ounce containers whole-milk ricotta
scallions, chopped
large egg, beaten
shredded low-moisture mozzarella
grated parmesan
Black pepper, to taste
salted butter
all-purpose flour
dry white wine
half-and-half
5-ounce package baby spinach, chopped
grated lemon zest
Green salad, for serving