In a small bowl, whisk together the cold water and gelatin. Let sit for 5 minutes to allow gelatin to soften.
Meanwhile, combine sugar, light corn syrup, 1/2 cup water, and salt in a small pot over medium heat. Fit a candy thermometer to the pot's side, ensuring it dips into the sugar mixture. Stirring continuously so the sugar doesn't burn, and cook until the mixture reaches 240℉ exactly. Remove from heat and pour into a heat-proof large liquid measuring cup.
In a stand mixer fitting with the whisk attachment, add the softened gelatin. Starting at a slow speed, gradually add the sugar syrup. Once all of the syrup has been added, increase the speed gradually and let run for about 15 minutes (or until cooled). The mixture should be fluffy and glossy.
Reduce the speed to low and add the vanilla and gingerbread spice to the marshmallows. Whisk until combined.
Generously dust an 8x12 pan with powdered sugar. Pour your marshmallow mixture on top and smooth the top. Generously dust the top of the marshmallows with powdered sugar. Place in the refrigerator uncovered overnight to set.
The next day, run a knife around the perimeter of the marshmallows and flip the pan to release. Cut into 20 large marshmallows or 40 small marshmallows. Serve and enjoy!