Pop each bag of popcorn as you normally would in the microwave.
We're going to work just one bag at a time right now: Transfer the popped popcorn from one bag to a large mixing bowl, doing your best to avoid pouring unpopped kernels into the bowl* (see my notes on this!)
In a microwave-safe bowl, add 6 ounces of the white candy bark/white chocolate and place in the microwave for 45 seconds. Remove, stir, and repeat for another 30-45 seconds. Stir, and if you need to add it to the microwave one more time, just try it for about 20 seconds. It'll likely be fully melted after the 2nd round in the microwave, though!
Drizzle about 1/2 of the melted candy bark onto the popcorn in the mixing bowl, stir, and continue drizzling the remaining melted candy bark and stirring until the popcorn is evenly coated.
At this point, if you're adding larger toppings such as peanuts, M&Ms, or even crushed cookies, go ahead and add them to the mixing bowl, stir, and then follow the next step.
Line a large cookie sheet with foil and then pour the candied popcorn onto the foil. Spread it out with the spoon/spatula you used to stir it.
If you're adding sprinkles to the popcorn, go ahead and add them now, stirring after the first coat and then adding a little more.
Repeat steps 2-7 with the remaining popcorn and white chocolate/baking bark. When you add the remaining 2 bags' worth of coated popcorn to the pan, make sure you continue to give the pan a little stir, just to prevent large clumps of popcorn from eventually forming after the candy hardens.
Once you've finished coating all of the popcorn, place the baking sheet with popcorn in refrigerator for about 10-15 minutes to allow the candy bark to fully harden on the popcorn. It will eventually harden on its own if you leave the pan out on the counter, it'll just take a while!
Remove from fridge, pull up both sides of the foil to make somewhat of a funnel and pour the popcorn into your serving dish(es) or into your storage bags/container if you're eating it later.
Enjoy with family and friends!