Combine the chocolate milk, cocoa powder, brown sugar, Biscoff spread, ginger, cinnamon, and nutmeg in a large saucepan.
Turn the burner on medium heat and cook while stirring occasionally until the sugar and Biscoff dissolve completely. Do not overcook and do not boil. You don't want to scald the hot chocolate.
Cook until the mixture is steaming and is warmed thoroughly. This should take about 5 minutes or so. One small tip is to remove a small amount of the hot chocolate with a ladle so you can test it prior to removing the saucepan from the heat. This allows you to check the flavour and the temperature in case either needs adjusting.
Next, remove the saucepan from the heat and pour the hot chocolate into mugs. I recommend filling each mug 3/4 full so there is still room for add-ins like marshmallows.
For a nice finishing touch you can top each mug with whipped cream, mini marshmallows, and some cocoa powder over top. Finally, add a cinnamon stick for stirring, and a gingerbread man for dunking.