In a large saucepan, bring 3 quarts of water and ¼ teaspoon of salt to a boil. When the water boils, add the pasta to the pot and boil for 8 minutes. Drain in a colander and run cold water over the pasta to cool it.
As the pasta is cooking, brown the Italian sausage in a skillet over medium heat, draining the grease when the meat is fully cooked and no more pink areas remain. Add the garlic and cook for another minute.
Stir the tomato paste and the can of diced tomatoes into the meat along with the basil, salt, and pepper. Bring the sauce to a boil and reduce the heat to simmer the sauce for about 5 minutes or until it is thickened.
Heat your oven to 350 degrees and spray a 9 by 13 baking pan with cooking spray.
In a medium-sized bowl, stir together the cottage cheese, 1 cup of mozzarella, and the Parmesan cheese. Beat the egg and stir this into the cheesy mixture.
Spread half of the meat and tomato sauce mixture in the bottom of the prepared pan.
Using a teaspoon, spoon the cheese mixture into the cooked manicotti. This may take some time, but use care to not tear the pasta noodles as you stuff them. Set each stuffed manicotti in the pan as you fill it, making two rows of noodles in the pan.
Top the manicotti with the rest of the tomato sauce mixture, spreading it to cover the noodles. Reserve the remainder of the mozzarella.
Bake the manicotti uncovered in the preheated oven for 30 minutes. Top the pasta with the reserved mozzarella cheese and bake it for an additional 5 minutes.
Let the manicotti cool for about 5 minutes before serving. To save the leftovers, cover the pan with aluminum foil and put it in the refrigerator for up to 5 days.
To reheat, you can either bake the whole pan, covered with foil, in a 350 oven for about 15 to 20 minutes, or you can microwave a single portion on a plate for about 45 seconds. You will probably want to cover the manicotti with a paper towel when you microwave it to avoid splatters.