Preheat oven to 375 degrees
Cook the pasta shells according to package. I generally deduct 3 minutes from cook time, because the shells cook further in the oven.
While pasta is cooking, heat the oil in a pan over medium heat, add the shallots for about 2 minutes, stirring occasionally, add in garlic for a few seconds.
Add the diced zucchini and carrot, stirring occasionally for about 5 minutes.
Add the spinach and cook down for about a minute. Set the veggie mixture aside to cool while preparing the cheese mixture.
In a bowl, combine the ricotta, 4 oz. grated mozzarella, parmesan cheese, egg, dried parsley, salt and pepper to taste. Add in the veggie mix, combine well.
To assemble, in a 9x12 casserole dish, spread ½ the marinara sauce in bottom of casserole dish.
Spoon the cheese mixture into each shell and place open side up in the casserole dish.
Cover shells with remaining Marinara Sauce. Sprinkle the remaining 4 oz. of grated mozzarella cheese over the shells.
Cover the casserole dish with foil and bake for 30 minutes. Sauce should be bubbling and cheese all melted. Serve immediately.