Very similar to "pimiento de padrón". Pan Blister... and sprinkle. Just follow the instructions.
Shishito are a little bit bigger. Therefore, cook it for a longer period of time.
Skillet on the fire at very high heat.
Add the peppers... Nothing happens but a small "clack clack" here and there
Shake the pan and you will see some black spots
Turn the heat down and add a good amount of olive oil and stir. It will smoke like crazy. If you have a lid for the pan use it now.
Keep shaking and mixing until they are cooked. A couple of minutes will do. Just test one before put them on the table.
Heavily on the salt. Fleur de sel will do.
They will wilt. Just shake it before you eat it to get the excess of salt off.
It's ok to leave the stems.