Preheat oven to 325ºF.
In a large bowl, beat butter, sugar, orange rind, orange oil and salt until fluffy.
Stir in flour and cornstarch to make a smooth dough.
Divide dough in half. Form into two logs. Wrap each log in plastic wrap and chill for 1 hour.
Slice logs into 1/3” slices. Place on parchment-lined baking sheets and bake for 15-18 minutes. Let cool.
Dip: In a double boiler, melt chocolate over simmering water. Dip half of the cooled cookies into the chocolate. Place on wax paper-lined baking sheets and chill for 30 minutes until firm.