I started sauteeing enough onions to make a large batch of soup. But then, when I went to the walk-in fridge, I realised that we were painfully short of the dark leafy greens that I wanted to use in said soup. It was going to be a riff on the classic Vichyssoise (potato leek soup), but instead of leeks, I used onions, and instead of plain potatoes, I was using potatoes, collard greens, and spinach, and then blending the lot together.
I also realised that I didn't have quite as many potatoes as I thought. This would mean that I had about triple the amount of onions that the recipe usually calls for. I cooked the onions down further than I normally would, and let them get a nice medium brown colour. I also added a bit of garlic to boost the flavours. When I added the last finishing touches, and gave the broth a taste, it was fantastic!
Then, when I finally pureed the lot of it together, I was in absolute heaven. All those extra onions gave the soup a really nice, bold taste. I'm not sure that I can do this every time, but once in a while should be fine.