A theoretical onion soup

This is one of my funniest cooking experiments that came out of a friendship in graduate school. My friend was from Serbia. She had traveled a lot, and was a walking encyclopedia. We both were living in Italy then, and away from home. I was struggling with daily life without knowing an Italian word. She became my translator. Soon I found myself digging into the magazine Cucina Italiana, and kept asking her to help me understand the recipes. With her broad knowledge, she knew all about cooking, but never cooked. I knew nothing about European cooking, but I loved the kitchen. So we formed a perfect cooking team of a theorist (she, a mathematician) and a practitioner (me, a computer scientist). She became my "cooking professor", and I became her "kitchen technician". 


One day, I asked her about the French onion soup. She gave me a recipe off the fly:


Recipe of "A theoretical French onion soup"


Ingredients:
- a few onions
- 1 egg yolk
- the crust of some hard cheese
- a little olive oil for browning onion
- a pot of water


Procedure: 
Slice onions and fry in olive oil until brown. Add water and boil until soft. Add crust of cheese and boil some more. When soup is done, beat one egg yolk in a bowl. Add soup slowly. Serve hot.


I loved this recipe. It was so simple. The next day, I bought 1 kilogram of onions and invited her to come over to my home to try out the recipe. She wasn't too excited, especially since she did not like onion smell at all. But I needed her badly to guide me through. I needed to figure out precisely how many onions qualified to be "a few", and whether "a little" oil meant a tablespoon or half a cup. Above all, I had never seen how onion soup looked like when it's done. So I needed her there to tell me when "done" happened. 

As it turned out, my friend made her lifetime discovery that browning 3 onions needed more than 1 drop of oil. Perhaps 2 tablespoons would do. It took us a few hours to discover that "when done" meant the onions had caramelized after hours of cooking, yielding a sweet and gentle flavor, which was heightened by the melted cheese crest. A good cheese would melt well and not stick to the bottom, leaving behind the hardest part of its crest. 

That evening's cooking was long. It was past 10pm when we sat down and ate. But we had the most satisfying experience ever with our onion soup. It was smooth and almost creamy. I liked it greatly. Even she liked it so much that she finished a whole bowl.

The downside of cooking onion soup is that the smell could stay in the house for a week. For this very reason, I don't plan to cook it again, no matter how satisfying it tastes.