Combine salt and pepper in a mortar and pestle or spice grinder. Grind until fine and well mixed. (Note 3)
Popcorn
Heat oil in a medium saucepan on medium-low heat, along with 3 popcorn kernels. Cover the saucepan.
Once the 3 popcorn kernels have popped, add in the rest of the kernels and cover the saucepan again.
As the popcorn is popping, periodically shake the saucepan to cause unpopped kernels to drop to the bottom. Also periodically uncover the saucepan, away from you, to release some of the steam.
Once the popping of the popcorn drops to once every couple of seconds, turn off the heat and empty popcorn into a large bowl.
Sprinkle over the salt and pepper seasoning, to suit taste, and toss the popcorn until well covered by the seasoning. (Note 4)
Notes
Can substitute sea salt with regular table salt.
Can substitute whole peppercorns with cracked black pepper or 1/2 tsp of ground black pepper.
If substitutions to salt and pepper have been made that are fine enough (not too chunky), you can skip the grinding process and just mix the salt and pepper together. I do still recommend grinding spices, if possible.
Some people find the amount of pepper overwhelming, so start with less of the salt and pepper seasoning and add more as needed to suit taste.