In a small bowl, stir together the caramel sauce and salt. 

Fill a shaker halfway with ice and add the eggnog, dark rum, and 1 Tbsp of the salted caramel sauce. Stir for 30 seconds. 

(Optional) Swipe 1 Tbsp of salted caramel sauce on the inside of the glass with the back of a spoon.

Pour the eggnog mixture into a glass and garnish with whipped cream and a drizzle of salted caramel sauce.