The issue is that it's easy to let the oil get to hot while you're chopping an onion. I also do the "prep while cooking" approach if I'm really pressed for time

The issue is that it's easy to let the oil get to hot while you're chopping an onion. I also do the "prep while cooking" approach if I'm really pressed for time or it's really simple, but it always turns out far worse. Some prep bowls and a bit of time to find things and chop before turning on the heat may make for more dishes to wash and take longer, but it certainly makes the food a lot more consistent and makes cooking less stressful. No more panicking that you've burned something while chopping up a garnish or letting a pot boil over because your back was turned getting something out of the pantry.