How to Make It
In a medium bowl, mix the lamb filling with the ricotta. Form the mixture into 2-inch balls. In a large skillet, heat the olive oil and cook the meatballs over moderate heat until browned all over, about 5 minutes.
Meanwhile, in a large saucepan, bring the marinara sauce to a simmer. Add the meatballs and basil sprigs, cover and simmer over moderate heat, stirring occasionally, until the meatballs are cooked through, about 15 minutes. Season with salt and pepper. Serve with grated cheese.