Brown paper bags are not necessarily designed to be microwave-safe. Watch the whole time when microwaving your popcorn, and if in doubt, it's better to err on the side of leaving some kernels unpopped rather than trying to pop every last one.
I have a weird sensitivity to certain sounds—there's no reason to go into the details except to say that I'm not generally inclined to make popcorn at home because I can't handle the high-pitched screeching of the pan as I shake it back and forth on the burner, tossing the kernels around so that none burn. I could invest in a popcorn device, like one of those air poppers, but I have enough stuff crowding my kitchen without adding a single-use item like that.
Fortunately, one of my colleagues told me that it's possible to make popcorn in the microwave in a brown paper bag—not the store-bought microwaveable stuff that comes pre-coated in flavors, but my own custom bag of popcorn. I wanted to come up with some fun popcorn flavors anyway, so I decided to test the method out at the same time.
Turns out it works! Here's how:
How to Make Brown Bag Microwave Popcorn
Start by tossing 1/2 cup of popcorn kernels with 1/2 teaspoon oil (I used a neutral vegetable oil) and salt. Then, dump the popcorn into a brown paper lunch bag and fold the bag top down.
In my first batch, the popcorn managed to push the bag open as it popped, so I started locking the corners of the bags by folding the corners down and tearing little tabs, then folding those tabs over. This prevents the bags from unraveling as the popcorn expands.
Then I pop it in the microwave and run it for about 2 minutes, though the exact time will depend on your microwave. A lot of people give the typical advice of letting the microwave run until the popping slows to about 2 to 3 seconds between pops. I tried that and almost lit a bag of popcorn on fire—seriously, it was smoldering.
Making popcorn is fun, but burning your house down isn't, so be sure to err a little on the un-popped side of things to avoid scorching and burning the popcorn: When you notice the popping slowing down just a bit, it's about time to stop the microwave. You'll end up with a few extra unpopped kernels, but they'll be at the bottom and can be separated easily from all the beautiful popped ones.
It's also important not to leave the popcorn unattended while it cooks. It didn't take long for mine to go from popping to smoldering, and it's not worth risking setting your microwave on fire by walking away from it while it's running. You'll want to keep an eye on it to be safe.
This is my ideal method. With no more horrible scratching sounds, I think I'll start making a lot more popcorn at home.
Serious Eats / Daniel Gritzer
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