It isn't surprising to find out that this soup is known all over the world, since it's basically warm milk. What's surprising is the number of people (in the USA, at least) who think their families are the only people in the world who eat it, my family included.
In researching this topic, I found soup made from all kinds of domesticated mammal milk, almond milk, soy milk and coconut milk.
The kind my family makes is very common in Byelorussia, Germany, Austria, Switzerland and Poland--and probably many countries I've neglected to reference. Poland alone has a wealth of milk-based soups. My family probably got it from the German part of our ancestry.
Some milk soups contain ham or bacon and potatoes and onion, some have egg mixed in, some have bread or buttered toast stirred in or floating on top, some have noodles, some have rice, some have noodles AND rice, some are sweetened with sugar!
One that I plan to try has a batter of egg, flour and water that's poured slowly into the boiling milk to make instant noodles.
My family just heats milk and butter and leftover spaghetti and serves it with salt, pepper and crumbled crackers. It's our go-to soup when we don't feel good, physically or otherwise; when we need comfort, this is soup is where the rubber meets the road.
Watch out, though--it makes you sleepy. Do not drive, handle heavy machinery, or sign important papers after consumption.
Marian Allen, Author Lady