To make the cups ahead, prepare the filling without the cranberries. Before serving, add the cranberries, fill the shells, and garnish.
You can use chopped fresh Italian (flat-leaf) parsley instead of the rosemary, and use the parsley leaves for a garnish.
To toast walnuts, sprinkle in ungreased heavy skillet. Cook over medium heat 5 to 7 minutes, stirring frequently until nuts begin to brown, then stirring constantly until nuts are light brown.