Evenly sprinkle gelatin over ¼ cup cold water. Set aside to bloom (soften).
Whisk egg yolks with a ½ cup sugar, until uniform.
Add salt and remaining ½ cup water and cook over a double boiler, stirring constantly, until mixture coats the back of a wooden spoon, about 8 minutes. Remove from heat.
Add gelatin to the custard, stir to dissolve, and pour thru a fine mesh sieve. Set aside to cool (do not refrigerate).
Using a hand mixer or stand mixer set to medium speed, beat egg whites until foamy. While constantly beating slowly add remaining ½ cup sugar, and continue to beat until soft peaks form. Stir in rum, brandy, nutmeg, and vanilla extract.
Once the custard is cool to the touch, thoroughly fold in the beaten egg white mixture and pour into your pie crust. Chill until firm, at least 2 hours.
Turn into pastry shell and chill.
When ready to serve, beat heavy cream, powdered sugar, and vanilla extract together until stiff peaks form. Top your Eggnog Chiffon Pie with whipped cream, be proud of yourself and serve to your awaiting party guests.