Preheat oven to 350°F with rack in middle. Generously butter baking dish.
Put bread in 2 shallow baking pans and bake, switching position of pans halfway through baking, until just dried out, about 10 minutes.
Heat 1 tablespoon oil in a 12-inch heavy skillet over medium-high heat until it shimmers, then cook half of sausage, stirring and breaking it into small pieces, until golden brown, about 6 minutes. Transfer with a slotted spoon to a large bowl. Brown remaining sausage in remaining tablespoon oil, transferring to bowl.
Pour off fat from skillet and wipe clean. Heat butter over medium heat until foam subsides, then cook onions, celery, garlic, and 1/2 teaspoon each of salt and pepper, stirring occasionally, until golden, 12 to 15 minutes. Add vegetables and bread to sausage.
Whisk together eggs, 1/2 cup cream, turkey stock, cheese, and parsley, then stir into stuffing and cool completely, about 30 minutes. Reserve 5 cups stuffing to stuff turkey and spoon remainder into baking dish, then drizzle with remaining 1/4 cup cream. Cover stuffing and chill.
About 1 hour before stuffed turkey is finished roasting, bring dish of stuffing to room temperature. When turkey is done, increase oven temperature to 425°F and bake stuffing, covered tightly with foil, until hot throughout, about 20 minutes. Remove foil and bake until top is golden and crisp, about 15 minutes more.
· Bread can be toasted 3 days ahead and kept (once cool) in a sealed bag at room temperature.
· Stuffing can be prepared (but not baked) 4 hours before roasting turkey.
· If baking stuffing at the same time as potatoes, put stuffing in upper third of oven and potatoes in bottom third (allow extra time).