First, prepare the marinara sauce. Set up a food processor and combine the mushrooms, tomatoes, garlic, carrots, onion and rosemary in its bowl. Run the processor until those aromatics become a lovely puree. Scoop out a 1/4 cup of the puree and set it aside for the filling. Then get out a large dutch oven or pot and heat the olive oil in it over medium high heat. Pour the aromatics in and let them become fragrant for a couple of minutes. The tomato paste and red wine go in next. Let them cook for another couple of minutes. Finally, add in the crushed tomatoes, salt, red pepper, oregano and bay leaves. Stir it all together well and bring it to a low boil. Then reduce it to a simmer and let it simmer for 2 hours.

While the sauce cooks, you can prepare the filling and cook the pasta shells. Get a large pot of water on the stove and bring it to a boil. Salt the water generously and cook the shells for about 8 minutes. Drain them and spread them out on a sheet tray or cutting board to cool. Set them aside. While the shells cook and cool, make the filling. Heat the olive oil in a large skillet over medium high heat and add the 1/4 cup of aromatics you set aside. Let it get fragrant for a minute. Then add the sausage and break it up as it browns. Season the sausage with the salt, crushed red pepper, garlic powder and dried oregano as it cooks too. When it is almost done, stir in the tomato paste and let it cook for another minute.

Take the skillet off of the heat and let it cool. While it cools, combine the ricotta, parmesan and egg in a large bowl. Add in the cooled sausage mixture and stir it all together thoroughly to make the filling. Cover it and refrigerate it until you are ready to make the stuffed shells. When the sauce is done, it's time for assembly. Take it off of the heat, remove the bay leaves, pre-heat the oven to 350 and get out a 9 x 13 baking dish. Pour a generous layer of the marinara sauce in the bottom of the dish. Then get out the filling and generously stuff the shells with it before nestling them into the sauce as you make them. Pour another generous layer of marinara sauce on top and finish by sprinkling the shredded mozzarella on the very top.

There may be a lot of marinara sauce leftover. Either refrigerate it or freeze it until you want to use it for another dish! Cover the baking dish with aluminum foil and bake the stuffed shells for 30-35 minutes. It should get bubbly and gorgeous. Take it out and serve immediately with crusty bread! It makes great leftovers as well.