Place oil in a tall pot over medium heat and add the popcorn kernels. Cover the pot with the lid, leaving it slightly ajar. The kernels will start popping after a bit. Keep the pot over the heat until the popping slows down. When you check inside the pot, the kernels should be popped. Turn off the heat. (See notes if you want to use microwave popcorn bags instead.)
For the Chocolate-Drizzled Popcorn
Line a 13x18 baking sheet with wax paper. Pour the popcorn onto the baking sheet and carefully remove and discard any unpopped kernels with a spoon. (The kernels will be hot.) Sprinkle the popcorn with the salt (unless you're using microwave popcorn that's already salted). Using clean hands, mix the salt and popcorn together. Spread the popcorn out evenly.
Place a heaping half cup of semi-sweet chocolate chips in a microwave-safe bowl, covered with a piece of wax paper. Heat for 30 seconds, then stir. Heat it for another 30 seconds and stir. You may need to heat it for another 20 seconds or so to finish melting it, depending on your microwave. Stir the chocolate until it is smooth. Dip a fork into the chocolate and drizzle it all over the popcorn. If you twirl the fork a bit, you will get thin ribbons.
Melt a heaping half cup of white chocolate chips in the microwave using a different bowl, but following the same process as before, stirring it after 30 seconds, etc. Dip a clean fork into the melted white chocolate and drizzle it over the popcorn. Let the chocolate dry. (It takes at least 30 minutes for the chocolate to dry using the chips, but candy melts dry faster.)
When the chocolate is dry, it's time to flip the popcorn over and drizzle chocolate on the other side. (I place a clean sheet pan over the popcorn, and invert the popcorn onto the clean pan.)
In the microwave, melt another heaping half cup of semi-sweet chocolate in your chocolate bowl from before. Use your chocolate fork to drizzle on the melted chocolate over the popcorn.
Melt another heaping half cup of white chocolate chips in the microwave, using your white chocolate bowl from before. Dip your white chocolate fork in and drizzle the white chocolate all over the popcorn. Let the popcorn dry before storing it. (You can refrigerate it for a bit to speed up the process.)
Store at room temperature in a sealed container or twist-tied plastic cellophane bags for 3-4 days. It might stay good for up to a week, but the popcorn is usually devoured before then.
The recipe is written for 20 cups of popped popcorn, in case you want to buy it already popped.If Using Microwave Popcorn:Pop two bags of microwave popcorn (one at a time), according to package directions. Use 1 ½ bags of popped corn for this recipe (unless you want to use more chocolate and all the popcorn.) You won't need to add salt or oil, since it will be seasoned already.How long does it take for chocolate to dry?It will take at least 30 minutes for drizzled chocolate to dry and harden. Keep in mind, you'll need to let the first side of the popcorn dry before flipping it over and applying the remaining melted chocolate. Then you'll need to allow another 30 minutes for that side to harden.Make ahead: This can be made 3-4 days in advance of serving it. If making chocolate-drizzled popcorn for an event, I'd make it no more than 2-3 days ahead of time, in case guests bring theirs home to eat the following day.Use themed cellophane treat bags to use the popcorn as party favors or gifts.