Add vodka, seal and let sit to infuse, 1 week. (The liquid will turn black.) Make simple syrup: In a saucepan over medium heat, simmer sugar and water until sugar dissolves. Let cool completely.

Stir in the cordial just before the syrup reaches this temperature (after 15-20 minutes). The mixture will bubble up, so be careful as it is very hot. Once the correct temperature has been reached ...