In a medium-sized pot, add the sugar, cornstarch, salt, and cinnamon. Whisk to combine. Slowly whisk in the eggnog making sure there are no lumps. Whisk in the eggs until fully incorporated.
Turn heat on to medium, whisking constantly until thickened, 5-8 minutes. Pudding should coat the back of a spoon. Immediately pour into a medium-sized bowl, add plastic wrap so it touches the top of the pudding. Place in the fridge for 3 hours until set.
Preheat oven to 350 degrees. Place everything in a large bowl, with a hand mixer beat on low for 30 minutes to combine. Beat on medium speed for one minute, the batter will resemble marshmallow fluff.
Fill cupcake liners 1/2 full. Bake 12-14 minutes until a toothpick inserted in the center comes out clean. Place cupcake tin on a wired rack, cool for 10 minutes. Take cupcakes out and let cool completely. Cupcakes have to be completely cool before adding filling and topping.
With a stand mixer or hand mixer, place the whipping cream in a large bowl. Slowly add the powdered sugar at slow speed. Whip until soft peaks form.
Add the cornstarch, vanilla, and cinnamon. Whip until cream will stand up on its own, hard peaks. Do not over beat or you will have butter!
Pipe eggnog pudding into the center of the cupcakes, top with whipped cream and garnish with more ground cinnamon or freshly ground nutmeg.
I suggest starting with making the filling, then the cupcakes, then the whipped cream. The pudding filling needs to set up in the fridge for 3 hours before filling the cupcakes.