hi squirrel, I've done this before but you need to staple it where you have folded it over (x 2, don't worry - no sparks!) or if you don't like the idea of the staples, stand it upright in the MW.
off the internet: "A regular paper lunch bag with ¼ cup of popcorn in the bottom (if desired, add ½ tsp of olive oil and a bit of popcorn salt), fold over twice and stand up in the microwave. Microwave until popping slows down to a couple pops per second"
There is a great recipe in the "Lunch Box & After School Ideas" booklet p4 for Popcorn Brunch Bars - perfect, only way to make it!
