Par-cook the pasta: Most jumbo shell packages will have cooking instructions for stuffed shells, but if not, cut the cooking time of the pasta in half, then add two minutes. Make sure to cook the shells in a large pot with plenty of (salted) water and stir occasionally to prevent sticking. Once the noodles have finished cooking, carefully drain them and rinse with cold water, then lie each shell out on a clean baking tray to prevent sticking.
Make the Ricotta by adding all ingredients to a food processor and processing until smooth and creamy, 45 to 60 seconds. Transfer the ricotta to a bowl and fold in the freshly chopped basil, reserving a few leaves to sprinkle on top after the shells bake.
Stuff the Shells: Add 1 cup of marinara sauce to the base of a 9 x 13" pan and spread it around evenly with a spatula. Use a spoon, cookie dough scoop, or piping bag to fill each shell, gently close it, then place it cut side-up in the pan. The amount of ricotta needed will vary on the size of the shell; I used gluten-free shells and used around 2 tablespoons for each shell.
Cover the shells with the remaining marinara and parmesan cheese, if using, then bake in the middle rack of the oven for 30 to 35 minutes, until browned and bubbly. Top with additional fresh basil, then serve warm.
This recipe doesn't call for many ingredients, so purchase the highest quality ones that you can.
If you'd like to you can also add up to 6 ounces of frozen spinach to the mix for extra veggies! Just be sure to thaw it completely and squeeze as much of the extra liquid out as possible