Cook apple cider over medium heat and boil down until it measures 1/2 a cup.
Meanwhile, oil an 8 or 9 inch square pan and generously coat with powdered sugar.
In a large sauce pan with high sides, combine the sugar and 1/2 cup of water.
Place pan over low heat and stir until sugar melts.
Once the sugar has melted, turn up the heat to medium high, stop stirring and instead, carefully swirl the pan every couple of minutes.
Cook the sugar until it caramelizes to a nice golden brown. Turn off the heat and slide the pan off the hot burner.
In the bowl of an electric mixer, combine 6 tablespoons water and the gelatin and let bloom for 5 minutes.
Add reduced apple cider, corn syrup, salt, cinnamon and ginger to the pan with the caramel and stir to combine.
Fill a small cup with water and pull out a pastry brush.
Put the pan back on the burner and attach a candy thermometer.
Turn the heat on to medium high and let boil without stirring.
Wipe down the sides of the pan with the pastry brush every minute or two.
Cook until the thermometer reaches 235F.
Turn off the heat and stir in the vanilla extract. The mixture will boil up, so be careful.
With the mixer running on low speed, drizzle the syrup into the mixer bowl. with the gelatin.
Turn up the mixer to high speed and beat until doubled in size, about 10-15 minutes.
Pour marshmallows into prepared pan and spread with an offset spatula.
Sift a little powdered sugar io top of the marshmallows and let set up for 8 hours or overnight.
Sprinkle a cutting board with powdered sugar and turn out marshmallows onto the board.
Fill a bowl with very hot water and get a clean tea towel. Also get out two chefs knives. (If you don't have two, its okay. It will just take a little longer to cut the marshmallows).
Place your knives in the hot water.
Pull out one knife and dry it off.
Cut off the rough outer edges of the marshmallows, switching knives when the first knife gets too sticky.
Slice the marshmallow slab into 8 strips, alternating knives as needed.
Cut the strips into eight cubes.
Dredge the marshmallows in powdered sugar to cover the sticky sides.
Place marshmallows in an airtight container until ready to serve.
Notes
Don't discard the marshmallow edges. They aren't pretty, but still tasty. Add them to coffee, brownies or sweet potato casserole.