Using a popcorn popper or a pot on the stove, pop the popcorn kernels in 1/2 cup batches to prevent burning. Separate out the unpopped kernels by moving the popped kernels from one large bowl to another, carefully, shaking from time to time to settle the unpopped kernels. You don't want any unpopped kernels in the mix, or someone could break a tooth.
In an extra large metal or wooden mixing bowl, combine the popcorn and Crispix. Toss to mix evenly.
Make the caramel
In a medium sized pot, melt the butter over medium-high heat. As soon as its melted, add the cocoa powder and whisk together. Then add the corn syrup and brown sugar and quickly whisk only just until everything is combined. Don't overwork it.
Let the caramel come to a bubble. Don't touch it during this time. Once the entire pot is bubbling, set a timer for 2 minutes.
After two minutes, add the sweetened condensed coconut milk and gently fold into the mix. This caramel doesn't behave like standard caramel, so you don't have to worry as much about crystallization and graininess, but try to be light-handed even still.
Once combined, bring to a bubble again. As soon as the entire pot is bubbling, set a timer for 4 minutes.
Make the caramel corn
As soon as the 4 minutes are up, pour the caramel directly over the popcorn/Crispix (be sure you're using a heat-proof bowl). Stir the mix together using a spoon around the edges of the bowl and folding everything back in gently. Try not to get too rough, or all the cereal will break up.
Add the crushed candy canes and flake salt, and stir again. Let sit for 10 minutes.
Add the white and dark chocolate chips, then stir again until just combined. Lay out on a large layer of foil on the counter to cool for at least an hour so the chocolate can set. Cover loosely with foil if it'll be out longer than that.