Put all the tomato sauce in a pot and bring to simmer on a stove, add chopped garlic in, add little bit of salt to taste
Cook the pasta 75% way, almost done but still firm.
To make the filling , place a bowl, mix ricotta cheese with 1 tbsp. of frozen spinach. While we mix, preheat the oven to 350 degree Fahrenheit.
Next, we're going to take 1 tbsp. of the filling and put that in to the pasta shells, place them in the container.
Cover the pasta with some tomato sauce, the topping will be some of the mozzarella, and the parmesan cheese.
Cover with a foil and bake for 45 minutes, after that, uncover, let it cool for 5 minutes and we ready to serve ! ( You could sprinkle with some parmesan cheese if you want ).