Custard - How much milk can one egg set?

It really depends on how thick you want it. Some sites recommend one egg or 2 yolks per cup of milk. Ruhlman mentions 2 eggs per cup as 'standard', with 1 egg able to thicken 3/4 of a cup of liquid (but more fat helps).

I can't comment on thickness of creme anglaise -- I had to gave up dairy years ago, and that's not something that I've ever made.

My understanding (from school days, Mrs Crabtree would be surprised) is that 1 medium egg will set 1/4 pint UK. That's 5 fl oz UK. USA is different and metric different again.

I use 1 FRESH medium egg to set 150mls of milk.

Just checking this out for a class I am teaching and confirmed with a quick look at 'Cooking Explained' Barbara Hammond, Longmans 1966, and yes, she says 2 meium eggs to half a pint (UK measures), 4 to 5 pz shortcrust pastry and a 7 ins sandwich tin to bake it in.

If its a pouring custard (creme anglaise ) 1 egg o half a pint creamy milk or light cream.