In a large saucepan, heat the oil until shimmering. Add the garlic and cook over moderate heat until lightly browned, about 1 minute. Add the carrots, celery and onion and cook, stirring, until softened, about 10 minutes. Stir in the chicken livers and sage and cook, stirring occasionally, just until the livers lose their pink color, about 3 minutes. Add the ground veal, pork and lamb and season with salt and pepper. Break up the meat with a wooden spoon and cook over high heat until no trace of pink remains, about 8 minutes. Pour in the wine and cook over high heat, stirring, until reduced by half, about 15 minutes.