Combine all the ingredients in a medium saucepan, bring to a simmer over medium-high heat. Reduce heat to medium-low, cover and simmer for 25 to 30 minutes, while you work on the meatballs.
Make the meatballs
Preheat your oven to 425°F
Combine all the ingredients for the meatballs in a large mixing bowl and knead well with clean hands, until fully combined. Do not overmix or meatballs will be tough.
Form into 15 to 18 meatballs, roughly the size of a squash ball (a large spring-loaded ice cream scoop really helps to do this quickly and efficiently).
Place a heavy bottomed skillet over medium heat and add a few tablespoons of cooking fat or oil to it. Once hot, sear the meatballs in batches, about 6 to 9 at a time, until they get nice and browned all around, then transfer them to a plate while you work on the rest of the meatballs.
Assembly
Once all the meatballs have been seared, cover the bottom of a 9" x 13" lasagna baking dish with a thin coat of the marinara sauce. Delicately arrange the meatballs in the dish and then top with the rest of the sauce.
Mix all the grated cheeses together and sprinkle over the sauce. Cover the dish with foil and bake in the oven for 25 to 30 minutes, until the cheese is fully melted and the sauce is bubbling on the sides.
Remove the foil, set the oven to broil and place the dish under the broiler until the cheese starts to bubble and turn golden, about 1 minute.
Remove the pan from the oven and allow the dish to rest for 5 to 10 minutes before serving. Garnish with a handful of chopped parsley and serve with your favorite pasta, cooked rice or with a side of steamed green vegetables (broccoli or green beans are my personal faves)