It's a common mistake. Just this weekend I followed a recipe from a well known cooking website for beef stroganoff that said to brown the beef in batches together with batches of onion. That's not a good idea, the onion will release liquid which prevents the beef from browning and once that cooks off the heat required to brown the meat will burn the onion. So I cooked the beef and onion separately instead. The onion can easily be cooked in one big batch, and if you take care not to burn the fond built up by the beef you can deglaze it with the onion. It's a good way to add extra flavor to the finished dish.

I also had a discussion with a roommate once, he criticized my way of cooking pasta. I keep it just barely boiling, but he insisted I should crank it up to max. I explained that it doesn't matter, the water won't get any hotter. I'll just waste electricity making steam. He didn't believe me so I got a thermometer and proved it.

If you want liquid water to go above 100C you need a pressure cooker.