I saw a chef in a past forum put up half and half as being half milk and half heavy cream, I didn't find it the first time I searched. That makes sense I think since heavy cream is 30% fat and the recipe I have which is also in French calls for 11.5 % fat. I don't have half and half available, so that is the problem. So, gonna try that...half cream and half milk. Water seems too light.
1/2 and 1/2 is the equivalent of single cream and light cream.
It was traditionally made by taking fresh, un-homegenzed milk, skimming the cream off of it, then recombining that cream with an equal amount of just-skimmed milk. In short, 1/2 and 1/2 is half cream and half milk.
As I understand it, the modern commercial process for making 1/2 and 1/2 is a little more sophisticated. But we can still make our own in the same time honored way of mixing cream and milk. Whatever. It's plus ca change or cuanto mas cambian las cosas -- no matter how you spell it.