Preheat the oven to 375 degrees F. Saute the sausage in a large heavy skillet over medium-high heat until cooked through, crumbling coarsely with the back of a spoon, about 10 minutes. Using a slotted spoon, transfer the sausage and drippings to a large bowl. Melt the butter in the same skillet over medium-high heat. Add the leeks, apples, celery and poultry seasoning to the skillet and saute until the leeks are soft, about 8 minutes. Mix in the drained cranberries, sage and rosemary. Add the mixture to the sausage, then mix in the croutons and parsley. Next add the chicken stock a little at a time until the stuffing is very moist. Be sure not to overdo it; it shouldn't be mushy. Season with salt and pepper. Place in a casserole dish. (The stuffing can be made to this point 2 days before Thanksgiving, refrigerated.) Bake in a 14-inch oval or 9 by 13-inch rectangular casserole dish and place, uncovered, in the oven for 20 to 30 minutes, until the top is crispy and the center piping hot. Remove and serve immediately. *Cook's Note: If stuffing a turkey, the stuffing must be cold before being placed in the bird.