In a medium saucepan, combine the whole milk, heavy cream, and pumpkin puree. Place over medium-low heat, stirring occasionally, until the mixture is warm but not boiling, about 5 minutes.
In a separate mixing bowl, whisk together the egg yolks and granulated sugar until the mixture is light yellow and slightly thickened, about 2-3 minutes.
Slowly pour the warm pumpkin mixture into the egg yolk mixture in a thin stream while whisking constantly to prevent the eggs from scrambling.
Transfer the combined mixture back into the saucepan and return to low heat, stirring continuously for about 5-7 minutes, or until it thickens enough to coat the back of a spoon.
Remove from heat and stir in the vanilla extract, ground cinnamon, ground nutmeg, ground ginger, and a pinch of salt until fully incorporated.
Allow the eggnog to cool at room temperature for approximately 30 minutes, then transfer to the refrigerator and chill for a minimum of 2 hours.
To serve, pour the chilled eggnog into individual glasses, top with whipped cream, and sprinkle with ground cinnamon or nutmeg.