Preheat the oven to 350ºF. Line muffin pan with baking cups (12).
Using the paddle attachment, beat the butter and sugar on medium speed until smooth.
Add the egg whites slowly, mixing until fully incorporated.
Sift the flour onto the butter mixture and add the chai tea powder. Mix until blended.
Add the eggnog and continue mixing until combined.
Using an ice-cream scooper, scoop the batter into the cups and bake for 20-25 minutes.
Remove from oven and cool.
For the frosting:
While the cupcakes are baking , fill a heavy duty pot about a quarter of the way with water and place on the stove over medium heat to simmer.
Add egg whites and sugar to the mixing bowl and place on top of the pot, ensuring the bottom of the bowl is not in contact with the water in the pot. Whisk the sugar and egg white mixture constantly, but gently, until temperature reaches 160°F.
Once at the correct temperature, remove from heat, wipe away the water from the underside of the bowl and transfer to the stand mixer. With the whisk attachment, begin to whip the meringue until it is thick, glossy, and the bottom of the bowl is no longer warm to the touch.
Switch from the whisk to paddle attachment and with the mixer on low speed, add butter cubes, one at a time, until incorporated. Continue to mix until it has reached a silky smooth texture.
Add vanilla beans and salt, continuing to beat on low speed until well combined. Then add the spiked chai eggnog latte and beat until combined.
Using a 6B French tip, pipe swirls onto the cupcakes and garnish with a little chai tea powder and nutmeg.