Preheat the oven to 325°F (170˚C). Line 2 baking sheets with parchment paper and grease with nonstick spray.
In a medium bowl, beat the egg whites and salt with an electric hand mixer until soft peaks form. Gradually add 2 tablespoons of granulated sugar and beat until stiff peaks form. You should be able to turn the bowl upside down without anything falling out. Set aside.
In a large bowl, mix together the eggnog, vanilla, and remaining ⅓ cup (65 G) sugar until incorporated. Sift in the flour and and fold with a rubber spatula to combine. Fold in ⅓ of the egg whites until incorporated, then add the rest and fold until just combined.
Transfer the dough to a piping bag or zip-top bag fitted with a medium round tip.
Working quickly, pipe 12 4-inch (10 cm) long and 1-inch (2 cm) wide cookies onto each baking sheet. Bake for 15-17 minutes, until lightly golden around the edges. Do not allow to get too dark.
Transfer the cookies to a wire rack and let cool completely. Use a sieve to sprinkle powdered sugar over the tops. Finish with a pinch of freshly grated nutmeg.