Preheat the oven to 375° F.

Cook the pasta shells in generously salted water according to the package directions for 7-8 minutes or just until al denté. Drain the noodles and set aside.

While the pasta is cooking, heat a large skillet over medium with the olive oil. Add the minced squashes, onion and one minced or pressed clove of garlic. Season with 1 teaspoon of the salt and pepper. Crush the thyme leaves between your fingers and sprinkle over the squash mixture, stir, and cook for 5 minutes or until the squashes are just barely becoming tender. Remove from heat and transfer to a mixing bowl to cool.

To make the cream sauce, wipe out the skillet, add the cream, the remaining garlic clove (peel and smash it with the side of a heavy knife), nutmeg and ½ teaspoon of the salt and bring to a low boil over medium high heat, stirring often. Reduce the heat to medium and cook for 10-12 minutes or until the cream has reduced by half. Stir in ½ cup of the Parmesan cheese and taste for seasoning.

Once the squash mixture has cooled, stir in the ricotta cheese, 1 cup of the mozzarella and ½ cup of the parmesan cheese to the mixing bowl. Whisk the egg in a small bowl and stir it into the cheese and squash mixture until combined.

Cover the bottom of a 9 X 12 baking dish with 1 cup of the cream mixture. Fill the pasta shells with a generous scoop of the ricotta and squash mixture and place the shells in rows until all are filled. Drizzle the rest of the cream mixture over the shells and top with the rest of the mozzarella. Cover with foil (spray with cooking spray so the cheese doesn’t stick!) and bake for 30 minutes or until bubbly. Remove the foil and bake for 10 more minutes or until the cheese begins to brown. Serve with more Parmesan cheese and chopped flat leaf parsley if desired.