Preheat the oven to 400ºF. Bring a large pot of water to a boil, then cook the shells according to the package directions.
While the pasta is cooking, add the tofu, miso, lemon juice, salt, basil, and oregano to a large food processor fitted with an S-blade. Process until very smooth, about 60 seconds. Stop and scrape down the sides, as needed.
When the pasta is done cooking, drain the noodles and rinse them with cold water to stop the cooking process. Pour 1 and 1/2 cups of marinara sauce into the bottom of a 9-inch by 13-inch dish, and spread it out evenly. Add a spoonful of filling into each cooked shell, then place the shell into the prepared baking dish. The fills do not have to be filled all the way-- 1 to 2 tablespoons per shell is plenty, so you'll have enough filling for the whole casserole dish.
Once you've filled most of the shells (I usualy have a few that break, or a few that won't fit) pour the remaining sauce over the shells and spread it out evenly so the shells are covered in sauce. Bake at 400ºF for 25 minutes, or unti the shells are piping hot.
Serve warm, with vegan Parmesan and fresh basil on top, if desired. Leftovers can be stored in an airtight container in the fridge for up to a week.
Nutrition information is for 1/4 of this whole recipe. This is automatically calculated, and is just an estimate, not a guarantee.