As far as I know no one made it from scratch back in the day, they just used the terrifying method of boiling unopened cans of sweetened condensed milk. (smittenkitchen.com)
Storage: store unopened cans of formula at room temperature. (amazon.com)
Nigel's mother (Victoria Hamilton) appears to have been the world's worst cook, boiling unopened cans of food to a soggy pulp and nervously refusing young Nigel's (Oscar Kennedy) suggestions that she try an occasional fresh veg. (rottentomatoes.com)