In May on Memorial Day, my brother-in-law gave me a number of herbs as a hostess gift. One of them was the African Blue Basil "Kasar" (Ocimum basilicum).
I believe it is mostly grown as a decorative herb, it is a bit bushy, grows fairly tall, 36" (90cm) and gives you beautiful spikes of purple-lavender flowers if you let it go to bloom. But... it is eatable and tastes like basil.
It is the easiest basil I've ever grown. Requires very little attention, grows fast and happily, survived a whole week in the summer without any water, and survived 2 light frosts. I live in zone 6, and the tag on the basil said hardiness zone 9-10.
If you snip off a stem and put it in water on the window sill, it will take less then a week to grow roots. When you put it in soil it quickly and happily grows a new plant. I'm a bit amazed at this basil's survival drive compared to other finicky basils that I've tried.
A couple of nights ago we had the temperature drop to 25 Fahrenheit (-4C) and the African Blue Basil finally died. It provided me with basil from May to November, isn't that amazing?
I was prepared for the frost and had a few cuttings in my kitchen. I just planted them in a pot to see if it will grow and provide me with basil over the winter.