Reading the Wikipedia pages on “Ghee,” “Clarified butter” and “Beurre noisette” has left me somewhat confused as to what ghee is. Some statements on the pages seem to suggest that it's always clarified butter, some that it's always beurre noisette, others that it can be either of the two depending on regional variations, and then it also might just be something in-between. Can someone clear up my confusion? Does it make (much) of a difference for cooking Indian recipes (I presume not, as ghee plays a less prominent role in a curry than beurre noisette does when it's used as a sauce).
Judging from those Wikipedia articles:
Clarified butter is rendered butter, which means that the solids are removed. Beurre noisette is browned butter, which contains the solids.
Ghee is slightly-browned (it should have a golden color) butter that is rendered. So you melt the butter till it's golden. Then you remove the solids by pouring the top layer into a container. So you have a combination (if you like) of clarified and browned butter.
I was doing some product demonstrations at an Asian market in Portland once, and an Indian vendor treated me to some of his samples brushed with a brownish ghee. I mentioned that I had never seen this kind of ghee before; I was used to a more yellowish, clarified-butter style.
He told me "Yeah, my wife hates it when I make this kind of ghee, but I prefer it because it has more flavor."
So, there's at least some anecdotal evidence that within the Indian ghee can vary in style from a simple clarified butter to a strained brown butter. His was slightly less brown than when I make a brown butter, but I suspect there's a broad continuum.
The primary distinction between ghee and beurre noisette is twofold:
In preparing ghee, every effort is made to ensure that all of the water is evaporated from the butter, so that it is has good long term storage properties. Evaporating the water is a side effect in making beurre noisette, and so it may or may not be fully purged, and room temperature storage is not recommended.
In preparing ghee, the milk solids are left behind (again, so that it has a long shelf life), and the product is essentially pure milkfat.
Any color imparted to ghee during the preparation is flavor and color compounds that have dissolved into the fat phase, as the milk solids are not part of the final product.
In beurre noisette, the browned milk solids and the flavor that they impart are the entire reason for making it, so they are included in the final product. The name reflects the color (as of hazelnuts) of the browned butter, due to the browning of the milk solids.
The only difference between buerre niosette, brown butter, and clarified butter is the milk solids are cooked longer... with clarified butter you stop the process before the milk solids get toasted (and sometimes remove the solids), brown butter they are toasted and black butter they are basically burnt. that's where the name comes from. Ghee is clarified butter traditionally boiled to clarify making it not brown or black... but technically all of them are ghee.