Herb and Apple Stuffing

4 tablespoons unsalted butter ( 1/2 stick)

2 cups medium-diced yellow onion (2 large)

2 cups medium-diced celery (3 large stalks)

2 Granny Smith apple s, unpeeled, cored and large diced

2 tablespoons chopped flat-leaf parsley

1 1/2 teaspoons minced fresh rosemary leaves

2 teaspoons kosher salt

1/2 teaspoon freshly ground black pepper

1 cup chicken stock

1/2 cup sliced blanched almond s, toasted, optional