Heat oven to 350°F. Line baking sheet with parchment paper.
In a stand mixer, combine butter with sugar and beat until fluffy.
Add eggs and vanilla, beat until creamy.
Now add flour, baking soda, cream of tartar, and salt. Mix well until dough forms.
Begin to roll dough into using 1 tablespoon worth of dough per ball.
Once balls are formed, roll each one in cinnamon sugar mixture.
Place sugar-coated balls on to lined baking sheet and press your finger into each one. Bake for 7-9 minutes.
Begin to make ganache filling by combining white chocolate chips with eggnog and rum. Microwave in 15-second increments stirring in between until chocolate is melted.
Begin to fill baked cookies with ganache mixture. Top each cookie with nutmeg. Allow cookies to cool and set for a few hours. Enjoy!