For the cookies:

1. Preheat the oven to 350*F. Cream the butter and the sugar together, then add the vanilla. Sift the salt and flour together in a separate bowl, and slowly combine with the butter, mixing until just combined.
2. Drop tbsp-sized cookie batter onto a baking sheet, leaving at least 1 inch between each cookie. Gently flatten with the bottom of a drinking glass or a spatula.
3. Bake at 350*F for 12 minutes, until the cookies are golden brown on the bottom. Allow to cool completely before icing.

For the vanilla icing:

1. Sift the confectioners sugar, removing all lumps. Add the vanilla and corn syrup, stirring until the icing is smooth and glossy.

For the chocolate icing:

1. Melt the chocolate chips, either in stages using the microwave or over a double boiler. Combine with the confectioners sugar and corn syrup, stirring completely until smooth and glossy.
2. Ice the cookies, half chocolate and half vanilla. Let sit for at least 15 minutes before serving, to allow the icing to set.