For a hot latte: Add the eggnog and chai concentrate to a small saucepan and heat over medium-low heat until steaming (do not boil). Remove from heat and pour into a mug. Garnish with whipped cream and/or nutmeg if desired and drink up!
For an iced latte: Add ice to a tall glass, then pour the chai concentrate and eggnog over the ice. Stir, then garnish with whipped cream and/or nutmeg if desired. Drink up!