Two
Is a unit of peanut considered to be one peanut or is a peanut actually two peanuts because one unshelled peanut has two nuts in it?
My reflection on this was that it had to be specified which one we were talking about. The Baker said that most people, especially for recipes, don't use peanuts as the unit, rather the volume that is needed. This is a great point. I struggle to come up with a recipe that calls for individual peanuts to be counted.
I think in everyday usage, a single peanut is referring to the nut outside of its shell. As this is the more popular method in which it is sold and consumed, I think it is fair to say that the shelled wins this time. Though if a situation presents itself where I am led to feel otherwise, I'll let you know.