1 Pour the milk and cream into a saucepan, add the spices (including the empty vanilla pod) and place on a medium heat. Bring to a simmer (but not boiling) and allow to cool for 5 minutes to allow the flavours to infuse.
Meanwhile, place the egg yolks and sugar in a large mixing bowl. Whisk well until light and thickened. Strain the warm milk into a jug through a sieve. Pour the spiced milk into the bowl of egg yolks in a steady stream, whisking well. Stir in the rum.
You can either place the mixture in a cooled sterilised bottle with a tight-fitting lid and allow the flavours to develop in the fridge. If you decide to do this you can freeze the egg whites in a sandwich bag until you’re ready to use, then defrost them in the fridge before whisking.
If you would like to serve straight away, place the egg whites in a large mixing bowl and whisk the whites to soft peaks.
Mix the demerara sugar and ground cinnamon on a plate. Have a small bowl of rum or water ready.
Fold the egg whites into the eggnog mix, then pour into a serving jug. Dip the rims of serving glasses into the rum or water, then dip straight into the sugar and cinnamon mix. Divide the eggnog between glasses and finish with a grating of nutmeg.