Method

Pour the milk and cream into a saucepan. Add the spices (including the empty vanilla pod) and place over a medium heat. Bring to a simmer (but do not boil) 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, then stir in the rum.
If serving later, place the mixture in a cooled, sterilised bottle with a tight fitting lid and allow the flavours to develop in the fridge. The egg whites can also be frozen in a sandwich bag until you’re ready to use, then defrosted in the fridge before whisking.
If serving immediately, place the egg whites in a large mixing bowl and whisk until they form soft peaks.
Mix the demerara sugar and ground cinnamon on a plate and prepare a small bowl of rum or water ready.
Fold the egg whites in to 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.