One of the best-loved features of a microwave oven is its ability to make popcorn fast and easy. But there are several caveats to that benefit. One is that you often have to monitor the popcorn to make sure you don’t under- or overcook it. You can press the “popcorn” button, but if the amount of popcorn in the bag doesn’t match the amount of time that the popcorn button is preset for, you’ll wind up with one of two things. One is a batch of underdone popcorn, with hard, tooth-crunching corn kernels scattered throughout the bag. The other is the acrid smell of burnt popcorn wafting through the house for the next few hours. New microwaves with multiple popcorn settings allow you to exactly match the cooking time to the bag size. You won’t have to interrupt your movie to make popcorn, and you won’t have to open windows to get rid of that terrible burnt popcorn smell.