1/2 cup water
3 tablespoons gelatin (3 packets)
2 cups sugar
1/2 cup eggnog
1/4 cup maple syrup
1 teaspoon vanilla extract
1/2 cup powdered sugar
1/4 cup cornstarch
Nutmeg for light dusting
Line an 8-x8-inch pan with parchment. Spray lightly with cooking spray. (A little spray underneath the parchment will also help hold it in place.)
Pour the water into the bowl of a stand mixer fitted with a whisk attachment. Sprinkle the gelatin on top; set aside.
In the meantime, place the sugar, eggnog, and maple syrup in a saucepan over medium heat; cook and stir until sugar dissolves. Bring mixture to a simmer and cook without stirring until candy thermometer reads 240°F, 8 to 10 minutes.
Pour the syrup mixture into gelatin mixture and whisk on low until combined. Once combined, increase speed to high and beat until thick and fluffy, and mixture triples in volume, about 10 minutes. Add vanilla and beat until well combined.
Using a lightly oiled spatula, scrape the mixture into the prepared pan. Use a lightly oiled offset spatula to smooth out top (top surface will not be completely even). Set aside to cool at room temperature for 8 hours or overnight.
Use a serrated knife and slice into 1-inch cubes. Whisk together the powdered sugar and cornstarch until well combined. Toss cut marshmallows in powdered sugar mixture. Dust with nutmeg. Marshmallows will keep in an airtight container for up to 5 days.