1 pound drained fresh ricotta
2 28-ounce cans Italian plum tomatoes, crushed by hand
1 teaspoon kosher salt
1 pound low-moisture mozzarella, 12 oz. cut in 1/4-inch cubes, 4 oz. shredded
2 cups grated Parmigiano-Reggiano or Grana Padano, freshly grated
3 tablespoons fresh Italian parsley, freshly chopped
¼ teaspoon peperoncino
1 large egg, beaten
6 tablespoons extra-virgin olive oil
6 garlic cloves, peeled and crushed
½ teaspoon crushed red pepper
1 pound large pasta shells
½ teaspoon dried oregano
8 ounces frozen peas, thawed
Preheat oven to 400 degrees F. Bring a large pot of salted water to boil for pasta. For the sauce, In a Dutch oven, heat olive oil over medium heat. Add garlic, sauté until edges are golden, about 2 minutes, then add the tomatoes. Slosh out the tomato cans with 1 cup hot water and add that to the pot. Stir in the salt, oregano and peperoncino and bring to a rapid simmer. Cook uncovered until thickened, about 20 minutes.
While the sauce cooks, add the shells to the boiling pasta water and cook until very al dente. Drain and separate onto sheet trays to avoid sticking.
For the filling, in a bowl, stir together the ricotta, peas, cubed mozzarellla, 1 cup grated Grana Padano or Parmigiano Reggiano, the parsley and egg. Mix the remaining shredded mozzarella and grated Grana Padano or Parmigiano Reggiano in a bowl and set aside.
In a 15-by-10-inch Pyrex or other large baking dish, spread 2 cups of the sauce. Divide the filling evenly among the shells and arrange in one layer in the baking dish. Top evenly with 2 cups more sauce. Sprinkle with the reserved grated cheese mixture. Dollop remaining sauce evenly over top. Tent with foil, bake until bubbly all over, about 25 to 30 minutes. Remove foil and bake until cheese is golden and crusty, 5 to 10 minutes more.