Bring a large pot of water to a boil and cook shells according to the packaged instructions.
Drain the noodles and transfer them to a large baking sheet, drizzling with olive oil to prevent sticking.
Preheat your oven to 350 degrees Fahrenheit.
In a mixing bowl, combine ricotta cheese, pumpkin puree, parmesan, egg, nutmeg, salt, pepper, garlic powder, and minced sage until smooth.
Mix together the jarred sauce with the remaining pumpkin puree and heavy cream until smooth.
Spread three-fourths of your sauce mixture across the bottom of a large baking dish.
Fill each cooled shell with about two tablespoons of the pumpkin-ricotta filling.
Arrange filled shells in your baking dish, cover with foil and bake at 350 degrees for about 30 minutes.
Remove the foil and sprinkle each shell with mozzarella cheese.
Return to the oven uncovered and bake for another 15 minutes until the cheese is melted and golden brown.
For an extra touch of crispiness, place under the broiler for just a few seconds.
Once done baking, serve these delightful Pumpkin Ricotta Stuffed Shells hot from the oven.