Give Your Roast Turkey an Italian Spin This Thanksgiving

Name: Give Your Roast Turkey an Italian Spin This Thanksgiving
Ingredients: 3 large onions, roughly chopped (about 1 1/2 quarts; 1 1/2 pounds; 680g), divided; 3 large carrots, peeled and roughly chopped (about 1 quart; 12 ounces; 340g), divided; 4 ribs celery, roughly chopped (about 1 quart; 12 ounces; 340g), divided; 12 thyme sprigs, divided; 1/2 tablespoon black peppercorns (1/4 ounce; 6g); 1 tablespoon fennel seed (1/4 ounce; 8g); 1 teaspoon (2g) red pepper flakes; 4 medium cloves garlic (3/4 ounce; 20g); 1/2 cup fresh sage leaves (1/2 ounce; 15g); 1 whole turkey (12 to 14 pounds total; 5.5 to 6.3kg), butterflied according to these instructions, backbone, neck, and giblets reserved; 2 tablespoons (30ml) vegetable oil, divided; Kosher salt and freshly ground black pepper; 1 1/2 quarts (1.4L) homemade or store-bought low-sodium chicken or turkey stock; 2 bay leaves