In a large mixing bowl, cream 1/2 cup butter or margarine, 1/2 cup sugar, and 1 teaspoon vanilla until light and fluffy. Add egg whites; blend well. Gradually add flour and blend well.
Drop batter by teaspoons 1 inch apart on an ungreased baking sheet. Spread with the back of a spoon into 3-inch rounds.
Preheat oven to 375 degrees F (190 degrees C).
Bake for 5 minutes or until edges are light brown. Working with 1 cookie at a time, loosen from baking sheet with a spatula and then quickly roll tightly around a pencil. Transfer to a wire rack to cool, seam side down.
With a pastry bag or soda straw or wooden pick, fill rolls with Creamy Chocolate Filling.
To Make Filling: In a small saucepan, melt chocolate and 1/4 teaspoon of vegetable oil (or butter or margarine) over low heat stirring constantly.