Boil a large pot of salted water and cook the jumbo shells according to package instructions until al dente. Drain and set aside.
In a large mixing bowl, combine cottage cheese, ricotta cheese, half of the mozzarella, half of the Parmesan, the beaten egg, chopped spinach, minced garlic, oregano, basil, salt, and pepper. Stir until everything is well incorporated.
Carefully stuff each cooked pasta shell with a generous spoonful of the cheese mixture. I typically use about 2 tablespoons per shell.
Spread a thin layer of marinara sauce on the bottom of a 9x13 inch baking dish to prevent sticking.
Place the stuffed shells in the baking dish, open side up, in a single layer. Pour remaining marinara sauce over the top, ensuring that all shells are covered.
Sprinkle the remaining mozzarella and Parmesan cheese on top.
Cover the dish with foil and bake in the preheated oven for 25 minutes. Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.
Once baked, remove from oven, let it cool for a few minutes, and garnish with fresh basil leaves before serving.
Notes
Feel free to add more vegetables or spices to the filling for extra flavor.