Put shishito peppers and a tablespoon of oil in a cast iron pan set over high heat
Don't stir the food until it starts to boil, which should take about one minute
Stir-fry the peppers and onion slices for about three to four minutes, or until the peppers are browned
Put them away and give them a little time to cool down before you cut the stems off
Put the cooked, stemmed, blistered shishitos and the rest of the ingredients into a high-powered blender or food processor. Blend or process until the mixture is smooth
Move to a jar or another container with a lid
Keep in the fridge for up to 5 days, or until you're ready to use it
