Sharing a recipe that scales nicely. This is my tried / tweaked recipe - but of course it is to my taste. 
1 fresh egg (large)
1 oz heavy cream
2 cups whole milk
1 oz bourbon/brandy/spiced rum - or other choice of alcohol
1 small stick cinnamon
1 tbs sugar or honey
grated nutmeg to top.
Simple instructions
Beat the cream until thickened then beat in the egg
Heat the milk to a boil with the cinnamon stick.
Dissolve the honey or sugar in it
Pour the hot milk into the egg & cream mixture in a thin stream and stir all the while - you don't want scrambled eggs.
Add your choice of alcohol
Leave to stand and cool - it will thicken
More involved instructions requiring another bowl but I believe tastes better
Separate the egg.
Beat the yolk into the cream after you've beat the cream until thickened
Beat the white separately until it forms soft peaks and fold it into the mixture before letting it stand and cool
Options
For a more eggy, richer or more alcoholically flavorful recipe - use 2 eggs, 2 oz of heavy cream and 2 oz of alcohol (in any combination)
Less sugary - use half or leave out the sweetener altogether. 1 cup of whole milk contains 13g of sugar and is quite sweet enough for some of us.
This recipe scales. i.e. you can double or triple it.
1 fresh egg (large)
1 oz heavy cream
2 cups whole milk
1 oz bourbon/brandy/spiced rum - or other choice of alcohol
1 small stick cinnamon
1 tbs sugar or honey
grated nutmeg to top.
Simple instructions
Beat the cream until thickened then beat in the egg
Heat the milk to a boil with the cinnamon stick.
Dissolve the honey or sugar in it
Pour the hot milk into the egg & cream mixture in a thin stream and stir all the while - you don't want scrambled eggs.
Add your choice of alcohol
Leave to stand and cool - it will thicken
More involved instructions requiring another bowl but I believe tastes better
Separate the egg.
Beat the yolk into the cream after you've beat the cream until thickened
Beat the white separately until it forms soft peaks and fold it into the mixture before letting it stand and cool
Options
For a more eggy, richer or more alcoholically flavorful recipe - use 2 eggs, 2 oz of heavy cream and 2 oz of alcohol (in any combination)
Less sugary - use half or leave out the sweetener altogether. 1 cup of whole milk contains 13g of sugar and is quite sweet enough for some of us.
This recipe scales. i.e. you can double or triple it.