Cook the pasta shells according to package instructions (just 9 or 10 minutes in boiling water). I like to make a couple of extra shells just in case any of them fall apart in the boiling water. Drain the water and place shells on a baking sheet until ready to use.
Preheat the oven to 400 degrees F. Spray a 9x13 inch baking pan with nonstick spray.
Pour ½ of the jar of Classico Riserva sauce into the pan and spread to cover the bottom.
In a medium bowl, combine the ricotta, cream cheese, half of the havarti or mozzarella and half of the Parmesan. Stir until well combined. Stir in the butternut squash and the sage. Add a good sprinkle of salt and pepper.
Fill shells generously with the butternut squash/cheese mixture and place in the prepared baking dish. Top the shells with the remaining sauce. Sprinkle remaining cheeses on top of the sauce.
Cover and bake for 35 minutes. Serve immediately. Leftovers are great too!