FOR THE SAUCE:
28 oz can whole peeled tomatoes (preferably San Marzano)
1/2 lb sweet Italian sausage (about 2 links)
3 tablespoons extra-virgin olive oil
1 large leek (white and green parts only), trimmed, halved lengthwise, rinsed well, and cut crosswise into thin half-moon slices (about 1 1/2 cups)
2 teaspoons chopped fresh parsley
1 teaspoon chopped fresh thyme
1 teaspoon chopped fresh marjoram
1 teaspoon minced garlic (about 1 medium clove)
1/2 teaspoon kosher salt, more to taste
freshly ground black pepper
FOR THE GNOCCHI
Package of gnocchi
1 cup freshly grated Parmigiano-Reggiano cheese (optional)
Make the sauce
1. Put the tomatoes and their juices in a food processor and pulse 4-5 times until the tomatoes are crushed but not completely pureed.
2. Remove the sausage from its casing and tear the sausage apart with your hands into coarse pieces. Heat 1 Tbs. of the olive oil in a 12-inch skillet over medium high heat. Add the sausage and cook, further breaking it apart with a wooden spoon, until lightly browned and almost completely cooked through, about 3-5 minutes. With a slotted spoon, transfer the sausage to a plate.
3. Add the remaining 2 Tbs. olive oil to the pan and then add the leek, parsley, thyme, marjoram, garlic and salt. Cook, stirring, until th eleek is soft and fragrant, about 3 minutes. Adjust the heat if the garlic or leek shows signs of burning.
4. Add the tomatoes and reserved sausage and stir well to combine, scraping up any browned bits on the bottom of the pan. Bring to a vigorous simmer and then reduce the heat to medium low. Cover the pan with the lid slightly ajar and simmer gently for 45 minutes. If the sauce is bubbling too fast, reduce the heat to low. Remove the lid and if the sauce seems watery, continue to simmer, stirring occasionally, until reduced to a thick sauce consistency. Adjust the seasoning to taste with salt and pepper.
Cook the gnocchi and toss with the sauce: Bring a large pot of well-salted water to boil over high heat. Wait until all the gnocchi float to the surface of the water, and then cook for one minute. Carefully drain the gnocchi in a colander. Transfer them to the sauce and gently toss to coat. Serve immediately, topped with Parmigiano if using.