Add the cooking oil to a medium sauce pot along with one popcorn kernel. Place a lid on the pot and then place the pot over medium-high heat. Allow the oil to heat until the kernel pops.
Once the single kernel pops, lift the lid on the pot, add the rest of the popcorn kernels, and replace the lid. Give the pot a vigorous shake back and forth to make sure all the kernels are coated in the hot oil. Let the pot continue to heat over medium-high, shaking the pot occasionally, until all the kernels are popped (or until you hear the popping slow to one kernel every 3 seconds or so).
Remove the pot from the heat and immediately pour the popped corn into a large bowl. Let the pot sit for a couple of minutes to cool slightly so the butter doesn't burn. Once slightly cooled, add the butter and sriracha to the pot. Allow the butter to melt then swirl it with the sriracha to combine.
Drizzle the sriracha butter over the popcorn in the bowl, then pour the popcorn back into the pot. Place the lid on top and give the popcorn a really good shake until all the kernels are evenly coated in sriracha butter. Return the coated popcorn to the bowl, sprinkle the nutritional yeast over top, then serve. Add salt if desired (I did not).
*Use a high heat cooking oil, like corn, grapeseed, canola, safflower, sunflower, or soybean.