In a medium-sized saucepan, pour in the ready-made eggnog and whole milk. Place the saucepan over medium heat, stirring frequently to prevent the mixture from scalding.
Carefully sift in the cocoa powder, whisking continuously until it's fully incorporated and forms a smooth, rich chocolate mixture without any lumps.
To enhance the flavors, add the maple syrup, vanilla extract, freshly grated nutmeg, and ground cinnamon to the saucepan. Stir thoroughly to blend all the ingredients evenly.
Continue to heat the mixture, stirring occasionally, until it's warm but not boiling, approximately 5 to 7 minutes. You want it steaming hot for the best flavor.
Once heated, remove the saucepan from the heat and allow the mixture to cool for a couple of minutes. Then, gently pour the delightful concoction into individual mugs or festive cups.
For a luxurious touch, top each mug with a generous dollop of whipped cream, allowing it to create a fluffy cloud on your drink.
To finalize your festive delight, sprinkle chocolate shavings on top of the whipped cream for an elegant garnish that's sure to impress.
Notes
Serve on a tray decorated with holiday ornaments for a festive touch.