If you decide to cook them whole simply skip to the next step. Otherwise using a small sharp knife cut of the top with the stem. Remove the seeds. You can speed up cleaning process by cutting the top part a quarter of an inch lower from the stem. This helps remove the seeds faster.Rinse peppers again in cold water to remove any remaining seeds.
In a large pan add generous amount of extra virgin olive oil, garlic cloves and peperoncino. Cook for 2-3 minutes. At this point you can add a couple of anchovies (optional) and stir until dissolved.
Add Italian frying peppers (whole or previously deseeded).
Cook on high heat for a few minutes then reduce to medium and cover with a lid. Cook for about 15 minutes or until tender.
Peppers should release enough juice while in the pan but feel free to add some water if the pan is getting too dry.
Once peppers are cooked add basil leaves, a splash of vinegar (see notes) and salt to taste. Give another good stir. Let vinegar evaporate and turn the heat off.
Serve with freshly ground black pepper or top them with crumbled feta cheese.
Notes
Add small amount of vinegar to start with, taste and add more if needed.