Set a saucepan on a low heat and add the milk, nutmeg, vanilla and cinnamon stick. Heat slowly continually whisking until the pan is just simmering. Turn off the heat and leave to one side.
In a mixing bowl, combine the egg yolks and sweetener and whisk using an electric hand mix until the yolks are pale yellow and thickened. This should take about 2 minutes.
Remove the cinnamon stick from the milk.
While whisking the eggs, slowly pour the hot milk into the bowl a little at a time. Make sure you add the milk really slowly to the egg mixture as otherwise it will overheat and scramble the eggs.
Once the milk and egg mix are smooth and fully combined, pour the mixture back into the saucepan.
Heat on a low heat and mix continuously until it has thickened and coats the back of a spoon. Draw a line on the back of the spoon with your finger. If the line stays visible it is the right thickness, if the line disappears then continue to heat a little longer. Remove from the heat and strain over a bowl using a sieve.
Whisk in the low fat double cream alternative and cover with cling film. Pop the eggnog in the fridge until chilled.
When the eggnog is chilled, serve it poured over ice and top with a little low fat aerosol cream and a sprinkle of dark chocolate.