1. To make the pasta: Bring a large pot of water to a boil and season with the salt. Cook the shells as directed, until al dente.
2. Drain the pasta and toss it with the oil. Spread onto a sheet pan and place in a blast chiller or fridge to cool.
3. To make the bolognese: In a rondeau over medium-high heat, warm ¼ cup of the oil. Add the beef and cook for 10 to 12 minutes, until it is fully cooked. Remove and drain the beef in a colander or china cap; reserve cooked beef in a pan. It should be well crumbled prior to draining the fat.
4. Return the rondeau to the stove over high heat and add the remaining ¼ cup oil.
5. Add the carrots and cook for 2 to 3 minutes.
6. Add the celery, onions, and garlic; cook for 2 minutes. Add the cooked beef, fennel seeds, bay leaves, oregano, and chili flakes. Bloom the spices for 2 minutes.
7. Add the tomatoes and wine to deglaze the pan. Cook for an additional 2 minutes, or until the wine is almost completely evaporated.
8. Remove from the heat and fold in the marinara and salt. Stir to fully incorporate.
9. Pour the filling onto a full sheet pan and let it cool in the walk-in for about 10 minutes, stirring halfway through the time.
10. Once the filling has cooled, mix in the mozzarella.
11. Using a large spoon, fill each pasta shell with bolognese.
12. In a greased 2-inch half hotel pan, ladle 24 ounces marinara in an even layer across the bottom. Place about 20 filled shells in the pan. Top with 8 ounces mozzarella, sprinkling it over the center of the shells. Cover with plastic wrap and foil and refrigerate. Repeat with two more pans.
13. Bake each pan in a 350°F oven for 25 to 30 minutes, until it reaches an internal temperature of 165°F.
14. Serve 4 shells on a plate with additional hot marinara. Garnish with Parmesan and fresh basil and parsley.