Stuffed Shells with Creamy Tomato Parmesan Sauce

1 splash cooking spray Ask a question about this ingredient

6 cups water, for boiling Ask a question about this ingredient

16 ounces jumbo pasta shells Ask a question about this ingredient

2 tablespoons olive oil Ask a question about this ingredient

3 cloves garlic, minced Ask a question about this ingredient

1 onion, diced Ask a question about this ingredient

1 1/2 pound ground beef Ask a question about this ingredient

1 dash salt Ask a question about this ingredient

1 dash cracked pepper Ask a question about this ingredient

1 tablespoon dried thyme Ask a question about this ingredient

2 cups ricotta, whipped with a fork Ask a question about this ingredient

2 eggs, beaten Ask a question about this ingredient

2 tablespoons unsalted butter Ask a question about this ingredient

1/4 cup flour Ask a question about this ingredient

2 cups milk Ask a question about this ingredient

1/4 teaspoon ground nutmeg Ask a question about this ingredient

1 dash salt Ask a question about this ingredient

1 dash cracked pepper Ask a question about this ingredient

1/2 cup parmesan, freshly grated Ask a question about this ingredient

1/2 cup marinara Ask a question about this ingredient

1 cup mozzarella, shredded Ask a question about this ingredient

1/4 cup fresh parsley, finely chopped Ask a question about this ingredient