Put a skillet on medium heat, add the maple syrup, vinegar and kosher salt and stir with a wooden spatula. Add in the walnuts and stir to coat them well.
Let the syrup come to a gentle bubble around the nuts, stir occasionally as the syrup reduces to a thick syrup, around 3-4 minutes.
Immediately transfer the nuts to a parchment-lined baking sheet, spreading them out evenly and making sure that no nuts are on top of each other. Sprinkle with flakey salt and let this cool at room temperature for 15-30 minutes to let the candy coating harden.
While those are cooling, put all your spices in a small, heat-proof bowl. Bring 1/4 cup of coconut oil up to 350°F and pour it over the spices. Stir to create a chili oil and set aside.
Add the remaining coconut oil to a large skillet with a tight-fitting lid. Put this on medium heat.
Add two popcorn kernels to the pan. When they pop, add the rest of the kernels, cover the pan and shake on the stove until all the kernels have popped, around 4 minutes.
Turn off the stove and pour the chili oil on top of the popcorn, top the pan with the lid again and shake to coat.
Serve with the popcorn and walnuts together in a large bowl!