It’s a Mrihani x Opalescent basil hybrid, I have about two dozen of these started with a variety of mutations. Most of them have mottled green (as well shown by the plant to the left) and all of them have a beautiful metallic purple shimmer to them. This gorgeous seedling is a beautiful example of a whorled phylotaxy, having four leaves per node instead of two.

I’m going to try to see if I can get this mutation somewhat stable, as it’s double your basil per basil, and who wouldn’t want that?