Heat the oil in a large pot with a lid on a medium setting. Add the popcorn kernels and cover.
Once the kernels begin to pop, shake the pot back and forth until the popping subsides. This should take just a few minutes.
Remove the pot from the heat. Pour over the melted butter and sprinkle over the chili powder, jalapeño and some salt to taste. Mix well to coat the popcorn.
Notes
Be very careful when chopping hot peppers that you don't touch your eyes before washing your hands!
Jalapeno popcorn is best when you pop fresh popcorn for the recipe, but you can use microwave popcorn if you like. Simply drizzle it with a small amount of butter after it's popped, and then add the chili powder and diced jalapeno.
If you prefer to use an air popper for your popcorn, that's fine too! Any way you like to make popcorn will work; the real deliciousness is in the seasonings here.
Butter can be replaced with extra virgin olive oil, or popcorn oil if you prefer.
Any style of popcorn kernels can be used as well. White popcorn tends to be smaller and more delicate, while yellow popcorn is sturdier and more flavorful.
The diced jalapenos will fall to the bottom of the bowl as you eat this. Be sure to reach down to the bottom while you snack to pick up some with each bite!
Don't try to make this delicious snack too far ahead of time! It's going to be most delicious and crisp if you serve it right away.