1. Combine breadcrumbs and milk in a large bowl and let sit 5 minutes. Combine carrot, onion, and mushrooms in a food processor and pulse until very finely minced, 10 to 12 times. Transfer to bowl with breadcrumb mixture, then add ground beef, egg, and salt and mix with hands until well combined. Form into 28 (1 1/2") meatballs.
2. Heat 1 tablespoon oil in a large nonstick skillet over medium-high heat until shimmering. Add half of the meatballs and brown all over, using tongs to gently turn, about 5 minutes. Transfer browned meatballs to a large plate and repeat with remaining 1 tablespoon oil and remaining half of meatballs, adjusting heat as needed to keep pan drippings from burning.
3. Drain fat from skillet and stir in marinara sauce, scraping up any brown bits from bottom of pan. Nestle meatballs into sauce and bring to a simmer over medium heat. Cook until meatballs are warmed through, about 5 minutes.
4. Meanwhile, bring a large pot of salted water to a boil. Add pasta and cook according to package instructions. Drain pasta and divide among bowls. Top with meatballs and sauce and serve with cheese on the side.
Source: Hannaford fresh Magazine, September - October 2018