Caramelizing onions, shallots, peppers, baby corns, scallions, etc. enhances flavor immeasurably.
It’s easy, however, to turn out dried, blackened food that wasn’t cooked until the caramelization turned into carbonization.
A solution to this problem also reduces fat in the process: use water with the fat you’re cooking them in.
Get the onions started in oil initially and bring up to temperature. Then, sprinkle water and cover to steam and soften the onions for a few minutes. This does not mean to boil them, but only just enough to contact the onions, transfer heat into them, and then evaporate. As the water evaporates, the oil or butter you added with it, or just then after it was nearly gone, will begin to do its job. Proceed to a golden brown color and you’re there!
Note that this isn’t a really good idea for mushrooms as they just end up boiled-looking.
Clarifying-only just means to stop the cooking process earlier. The onion bits should have lost some of their opacity without having actually benn boiled. It is usually not necessary then to introduce water into the process of clarification. If you have too much onion to clarify without resorting to water, then you’re pan is too small: cook in batches.
This is perhaps best explained while thinking about a couple of dishes that capitalize on the flavor of onion.
For a bœuf bourgignon or Stroganoff, you want to start by browning the meat first. Steak tips work well if you can cook them at low temperature long enough to release the collagen. Steak tips are less expensive than tenderloin (filet mignon).
After browning the steak and removing it, you’re left with the fond in the skillet. Add oil and a lot of finely slided onion and, optionally, sliced mushrooms.
Add salt. This pulls water out of the onions (and mushrooms) which concentrates the flavors. Cook on medium or medium low for about 10 minutes.