In a large bowl, whisk together the eggs, milk and melted butter. Gradually whisk in the flour and salt until the mixture is smooth. Refrigerate for 1 hour until slightly thickened.
Spray an 8-inch nonstick skillet with cooking spray. Place the pan over medium heat. With a small ladle, pour about 3 tablespoons of the batter into the pan. Turn the pan at a 45 degree angle to coat the pan evenly so the batter forms a perfect circle. Cook the crepe only until lightly browned, about 30 seconds. Turn the crepe over with a spatula and cook the other side only until lightly browned, about 30 seconds. Slide the crepe onto a 12-inch platter and continue the process with the remaining batter. Stack the crepes between waxed paper so they don't stick. You can prepare these crepes a day in advance covered in plastic wrap in the refrigerator. No need to reheat the crepes before filling and baking.
Make the ricotta filling:
In a large bowl, add all the ingredients for the ricotta filling. With a large wooden spoon or spatula, stir all the ingredients until well blended. Store covered in plastic wrap in the refrigerator until ready to use. You can make this filling the day before.
Make the marinara sauce:
In a large heavy nonreactive saucepan with a lid, heat the olive oil on medium heat. Stir in the onion and garlic and cook until fragrant but NOT browned. Add the crushed tomatoes to the pan and crush further with a potato masher. Simmer 30 minutes, slightly covered, on medium-low heat, stirring every so often.
Add the parsley, basil leaves and salt and pepper, to taste, and simmer for another 10 minutes until the sauce is slightly reduced. Taste and re-season as necessary.
Put it all together:
Preheat the oven to 375 degrees F. Coat the bottom of a 13 by 9-inch glass or ceramic baking dish with 1 cup of the prepared marinara sauce.
Spoon 3 tablespoons of the prepared ricotta filling 1 inch from the edge of a crepe. Roll evenly into a log, keeping the filling even as you roll. Repeat with the remaining crepes. Place manicotti seam side down and side by side in the sauced baking pan.
Spoon 1 to 2 cups of sauce over the top of the manicotti. Sprinkle with the grated Parmesan.
Cover the baking dish loosely with foil and bake about 20 minutes. Uncover and bake another 20 minutes until the topping is golden brown and sides are bubbling. Let rest about 15 minutes before serving to firm up the manicotti filling.