I'm following a method from America's Test Kitchen for caramelizing onions large batch in a crockpot. The first step is to microwave the onions and discard the liquid thrown. I'm going to make onion soup, so should I reserve this liquid? I's about 2 cups. I'm wondering if it will flavor the broth or it is not worthwhile. Now that I write this, I realize I'm just using carton beef stock, so this will only dilute the broth. But if I make from scratch in future shall I use it in place of some water?