When ready to cook, set Traeger temperature to 325℉ and preheat, lid closed for 15 minutes.

Transfer chicken livers to a cup that just fits the head of an immersion blender and purée until smooth. Heat olive oil in a large Dutch oven over high heat until shimmering.

Add ground beef, pork and lamb. Season with salt and pepper and cook, stirring to break up the meat with a wooden spoon. Cook until browned.

Remove from heat and stir in puréed chicken livers. Heat butter and pancetta in a large skillet over medium-high heat. Cook, stirring frequently until fat is rendered but butter and pancetta have not browned, about 8 minutes.

Add onion, carrots, celery, garlic, sage and ¼ cup parsley. Cook, stirring until vegetables are completely softened but not browned, about 8 minutes.

Transfer mixture to Dutch oven with meat mixture. Return Dutch oven to high heat. Cook, stirring until most of the liquid has evaporated from the pan, about 10 minutes longer. Add the wine and cook, stirring until most wine has been evaporated.

Add stock, tomatoes, milk and bay leaves. Season with salt and pepper. Bring sauce to a simmer, then transfer to Traeger.

Cook uncovered, stirring every 30 minutes until the liquid has almost completely reduced and sauce is rich and thick, about 3 hours.

Skim off most of the fat, leaving behind about 1 cup. Stir in heavy cream, Parmesan and ¼ cup parsley. Bring to a boil on the stovetop, stirring constantly to emulsify.

Season to taste with salt and pepper. Keep warm.

Cook pasta by package directions in a large pot of salted water until al dente. Drain and reserve a ½ cup of water. Return pasta to pot and add sauce to just coat the pasta as well as the ½ cup of reserved cooking liquid.

Place pot over high heat on the stove, tossing and stirring gently, until sauce is thick and pasta is coated, about 30 seconds.

Transfer to a serving bowl and serve immediately. Garnish with freshly grated Parmesan and additional flat-leaf parsley.