In the bowl of a stand mixer fitted with a whisk attachment, combine the gelatin and ½ cup of the cold water and let sit.
While the gelatin blooms, combine remaining water, sugar, corn syrup, Torani Puremade Hazelnut Syrup, and salt in a small saucepan. Cook over medium heat until the sugar dissolves. Increase the heat to high and cook until the syrup reaches 240 on a candy thermometer.
Turn the mixer on low and slowly pour in the sugar syrup. Increase the speed to high and whip until the mixture is very thick, about 15 minutes.
Generously dust a glass baking dish with powdered sugar. More is better here, in order to not have the marshmallows stick to the pan. Pour the marshmallow mixture into the pan and smooth the top. Dust with more powdered sugar.
Let sit uncovered overnight to let the marshmallows dry out to become less sticky.
Once set, turn the baking dish over onto a cutting board dusted with powdered sugar. Use a snowflake cookie cutter to cut out marshmallows, dusting with more powdered sugar as they are cut to prevent sticking.
To serve, place in your favorite cup of hot chocolate or simply eat as is.