If I had to describe this French Onion Soup in one word…Decadent. Slowly sautéing onions over 2 hours leads to a deep and rich caramelized flavor that’s then cooked with white wine and beef stock. Finally, it’s topped off with a rustic, toasted baguette rubbed with garlic, before being broiled with a gruyere and gouda cheese blend.
The Science Behind Caramelized Onions
Caramelization is the process of browning that takes place when sugar is heated. That is the most general idea behind this. Heating the onions causes a chemical reaction called pyrolysis. Chemically, it breaks down the larger starch and sugar molecules in the onion. Physically, the structure is changed from a yellow-white color to a caramel-brown color.
Because onions consist of about 89% water, it takes a long time for them to sweat. As they continue to sweat, the water in the stock pot will evaporate. This leads to the onions steady increase in temperature. Once they reach 212 degrees, the pyrolysis process begins. It is critical at this point to stir the onions every 5-10 minutes from here on out. At first. you can stir in 10 minute increments, but as they caramelize more you will want to keep a more watchful eye on them to ensure they don’t burn.
During the caramelization time, the larger sugar molecules in onions are broken down into smaller, simple sugar molecules. This is why caramelized onions have a sweeter taste than their raw counterparts. Your tastebuds don’t register the large sugar molecules; they acknowledge the simple sugar molecules.
Caramelizing onions can be a lengthy process and is definitely a labor of love, but you will surely impress all your friends and family with this amazing soup. If you need a reason to stay in and take it easy, just let your friends know you have to keep an eye on the onions while they are caramelizing!