Step 1

Preheat the oven to 350°F and set an oven rack in the middle position.

Step 2

Parboil the Manicotti Shells: Bring a large pot of salted water to a boil. Cook the manicotti shells for exactly 6 minutes (they will only be partially cooked). Drain well and rinse with cold water.

Step 3

Make the Filling: In a large bowl, beat the eggs. Add the ricotta, mascarpone cheese (or cream cheese), 1 cup of the mozzarella, 1 cup of the Pecorino Romano, the spinach, basil, garlic, oregano, and salt; mix until evenly combined. Transfer the filling to a pastry bag or large zip-lock bag. (If using a zip-lock bag, be sure the corners are square; the rounded-corner bags are difficult to use.) Twist and squeeze the bag so the filling is in one corner. With scissors, snip a ¾-inch opening in corner. Pipe the filling into both ends of the manicotti shells, filling until completely full.

Step 4

Make the Sauce: In a large bowl, stir together the marinara sauce and heavy cream.

Step 5

Assemble and Bake: Spread ¾ cup of the sauce into a 9x13-inch baking dish. Arrange the stuffed manicotti shells, narrow side up, over the sauce. Pour just enough sauce to cover the manicotti (you'll have about ¾ cup leftover; save it for serving). Cover the dish tightly with aluminum foil. Bake for 35 minutes. Uncover and top the manicotti with the remaining 1 cup mozzarella and ¼ cup Pecorino Romano cheeses Bake, uncovered, for 10 to 15 minutes more, until the cheese is melted and lightly golden. (To brown the cheese further, turn on the broiler and bake for a few more minutes, keeping a close eye, until the cheese is golden.) Let sit for about 10 minutes before serving. Warm the reserved sauce and pass at the table for anyone who would like extra.