Start by boiling a large pot of salted water. Once boiling, add the jumbo shells and cook them according to package instructions until al dente. Drain the shells and set them aside to cool slightly.
In a mixing bowl, combine the cottage cheese, 1 cup of shredded mozzarella cheese, grated parmesan cheese, pesto, and the egg. Mix until all the ingredients are well combined and creamy.
While you prepare the filling, preheat your oven to 375°F (190°C).
Spread a thin layer of spaghetti sauce on the bottom of your baking dish. Using a spoon or a piping bag, fill each jumbo shell with the cheese and pesto mixture. Place the filled shells in the baking dish, opening side up. Pour the remaining spaghetti sauce over the top and sprinkle the remaining 1 cup of shredded mozzarella cheese over the sauce.
Cover the baking dish with aluminum foil and bake in the preheated oven for about 25 minutes. After 25 minutes, remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden brown.
Once baked, remove the Pesto Stuffed Shells from the oven and let them cool for a few minutes before serving. Garnish with fresh basil or additional parmesan cheese if desired.
