Sprinkle gelatin over eggnog then heat over medium high heat in a small pot and simmer until gelatin dissolves. Add cinnamon then transfer eggnog to a small bowl and cover with plastic wrap, so the plastic adheres to the surface of the eggnog (preventing a layer of film from forming on the eggnog). Let the eggnog cool for 2 hours in the refrigerator until firm.
While that sets, make your tortilla twirls by cutting flour tortillas into quarters then roll up into a cylinder, securing the loose side in the center with a skewer, then lower into the frying oil (heated to 350F) until it crisps, frying on all sides. Transfer completed twirls onto a paper towel to absorb excess oil. Allow to cool fully before attempting to fill.
Beat refrigerated eggnog until whipped and smooth.
Whip heavy whipping cream to stiff peaks then fold in the eggnog mixture until a smooth mousse is formed.
Transfer the eggnog mousse into a piping bag with a star tip.
Once the tortilla twirls are cooled, pipe the mousse into the tortilla twirls.
Finish by garnishing with a dusting of powdered sugar.