These hands-off slow cooker meatballs require no searing, roasting or stirring, making them a great make-ahead dinner for busy weeknights and an excellent recipe to have in your backpocket for holiday houseguests. For the meatballs, we use a combination of beef and loose Italian sausage for a seasoning shortcut—the ground fennel is so good with the parmesan and fresh lemon zest. The meatballs simmer away in an easy tomato sauce that is inspired by Marcella Hazan’s iconic recipe. The butter gives the tomatoes a velvety richness and the quartered onion infuses incredible flavor while the sauce cooks. We call for discarding the onion before serving, but it makes an excellent snack for the cook when sprinkled with a little flaky sea salt.
Cooked pasta, polenta or toasted hoagie buns, for serving (optional)
In a large bowl, gently combine the beef, sausage, panko, parmesan, parsley, milk, egg, garlic, lemon zest, 1 teaspoon of salt and ½ teaspoon black pepper.
In a 5- to 7-quart slow cooker, drizzle some olive oil in the bottom of the insert. Using your hands or a 2-inch ice cream scoop, portion out the meatballs and arrange in the bottom of the slow cooker. You should have about 16 meatballs.
Using your hands, crush the tomatoes into the slow cooker and add their juices. Add the onion, butter, tomato paste, basil sprigs, dried oregano, crushed red pepper and a generous pinch of salt. Do not stir.
Cover the slow cooker and cook on HIGH for 4 hours or on LOW for 6 to 8 hours, until the meatballs are cooked through and the sauce has thickened. (If desired, you can stir the sauce halfway through cooking, but it is not necessary.) Discard the onion and basil sprigs. Gently stir the sauce and season generously with salt.
Serve the meatballs over cooked pasta, polenta or piled on a toasted hoagie bun. Garnish with freshly grated parmesan cheese and finely chopped parsley.
NOTE If your sausage blend does not contain fennel seed, then add 1 teaspoon crushed fennel seeds to the meatball mixture.
MAKE AHEAD The meatballs and sauce can be refrigerated for up to 2 days in advance or frozen for up to 1 week. Reheat gently on LOW in your slow cooker until heated through.