1) Preheat oven to 170deg;C / gas mark 3.
2) Put the stuffing cubes in a large bowl and set aside. Butter a 3-litre casserole dish.
3) Melt 30g of butter in a large skillet over medium-high heat. Add the sausage and break up with a wooden spoon. Cook until it loses most of its pink colour, but not so much that it's dry, about five minutes. Add the sausage and pan drippings to the stuffing cubes. Melt the remaining butter in the pan. Add the onion, apple, celery, and salt. Cook until the vegetables get soft, about five minutes. Add the stock and parsley and bring to a boil.
4) Pour the vegetable mixture over the stuffing cubes and toss until evenly moistened. Mix in the walnuts and eggs. Loosely pack the dressing in the prepared pan and cook uncovered until the top forms a crust, about 40 minutes. Drizzle about two tablespoons of turkey pan drippings or melted butter over the top. Cook until the top is crisp and golden, about 20 minutes more. Set immediately or warm.
Tips: Put the dressing in the oven during the last hour of cooking the turkey
Note: To toast nuts, spread them out on a baking sheet and toast in a 180°C / gas mark 4 oven until golden, about seven minutes.