The secret to a good French onion soup is the long slow cooking of the onions. You slice them then you cook them in butter at a low heat until the onions are really soft and just beginning to caramelize. That’s what gives French onion soup its incomparable flavor.
This soup starts with something like that. Onion, thinly sliced, cooked long and slow in butter until melt-in-the-mouth soft and lightly browned. When the onions had reached that stage, I poured in the broth, the cubed cooked meat and the squash. Ten minutes later, the spinach leaves went into the pot. Two minutes after that, it became this gorgeous soup.
What’s the idea behind adding meat and veggies to French onion soup? To be honest, I was sweating the onions and forgot about them. The next time I saw them, they were lightly browned already. Haven’t I said so many times that when something goes wrong never ever panic? So I told myself I might as well complete the process of caramelizing them.
And… guess what? The darn soup turned out so good.
So, from now on, when making soup, I’ll go beyond sweating the onions. I’ll cook them until they are the color of amber. Not only do they sweeten the broth in a most delicious way, they give it a deeper and richer color too.