Gently press mint (8-10 leaves or so) with simple syrup in a julep cup or equivalent. Add Cognac and Rye, preferably high proof (90-106) versions for historical accuracy. Stir gently. Add crushed ice to fill. Stir gently again to raise frost. Add more crushed ice mounding over top of cup. Garnish with mint and optional splash of dark rum. Drink through a short straw.