Combine milk and egg in a small bowl. Place breadcrumbs and if desired, sea salt in a shallow bowl. Dip ravioli in milk mixture, and coat with breadcrumbs.
In a large saucepan, heat marinara sauce over medium heat until bubbling. Reduce the heat to simmer.
In a large heavy pan, pour olive oil to depth of 2 inches. Heat oil over medium heat until a small amount of breading sizzles and turns brown. Fry ravioli, a few at a time, 1 minute on each side or until golden. Drain on paper towels. Sprinkle with Parmesan cheese and serve immediately with hot marinara sauce.